LONDON — Amid a flurry of missile tests and inflammatory rhetoric, the world’s attention is focused on North Korea's nuclear program.

But one expert believes the rogue state's stockpile of chemical weapons could also bring catastrophic consequences.

The Center for Nonproliferation Studies estimates North Korea has between 2,500 and 5,000 metric tons of chemical weapons.

In particular, it has a large supply of VX, the deadliest nerve agent ever created; last year it was used to assassinate Kim Jong Un’s half-brother, Kim Jong Nam, at Kuala Lumpur airport.

The chemical stockpile could harm thousands of people if it were attached to a missile or if it ended up in the hands of Islamist extremists, according to Hamish de Bretton-Gordon, former commanding officer of the U.K. Chemical, Biological, Radiological and Nuclear Regiment (CBRN) and NATO’s Rapid Reaction CBRN Battalion.

RELATED: As tensions rise, North Korea stages mass rally in Pyongyang

18 PHOTOS As tensions rise, North Korea stages mass rally in Pyongyang See Gallery As tensions rise, North Korea stages mass rally in Pyongyang A view shows a Pyongyang city mass rally held at Kim Il Sung Square on August 9, 2017, to fully support the statement of the Democratic People's Republic of Korea (DPRK) government in this photo released on August 10, 2017 by North Korea's Korean Central News Agency (KCNA) in Pyongyang. KCNA/via REUTERS ATTENTION EDITORS - THIS IMAGE WAS PROVIDED BY A THIRD PARTY. REUTERS IS UNABLE TO INDEPENDENTLY VERIFY THIS IMAGE. NO THIRD PARTY SALES. SOUTH KOREA OUT. NO COMMERCIAL OR EDITORIAL SALES IN SOUTH KOREA.? Servicepersons of the Ministry of People's Security met on August 10, 2017 to express full support for the Democratic People's Republic of Korea (DPRK) government statement, in this photo released on August 11, 2017 by North Korea's Korean Central News Agency (KCNA) in Pyongyang. KCNA/via REUTERS ATTENTION EDITORS - THIS IMAGE WAS PROVIDED BY A THIRD PARTY. REUTERS IS UNABLE TO INDEPENDENTLY VERIFY THIS IMAGE. NO THIRD PARTY SALES. SOUTH KOREA OUT. A general view shows a Pyongyang city mass rally held at Kim Il Sung Square on August 9, 2017, to fully support the statement of the Democratic People's Republic of Korea (DPRK) government in this photo released on August 10, 2017 by North Korea's Korean Central News Agency (KCNA) in Pyongyang. KCNA/via REUTERS ATTENTION EDITORS - THIS IMAGE WAS PROVIDED BY A THIRD PARTY. REUTERS IS UNABLE TO INDEPENDENTLY VERIFY THIS IMAGE. NO THIRD PARTY SALES. SOUTH KOREA OUT. NO COMMERCIAL OR EDITORIAL SALES IN SOUTH KOREA.?? Servicepersons of the Ministry of People's Security met on August 10, 2017 to express full support for the Democratic People's Republic of Korea (DPRK) government statement, in this photo released on August 11, 2017 by North Korea's Korean Central News Agency (KCNA) in Pyongyang. KCNA/via REUTERS ATTENTION EDITORS - THIS IMAGE WAS PROVIDED BY A THIRD PARTY. REUTERS IS UNABLE TO INDEPENDENTLY VERIFY THIS IMAGE. NO THIRD PARTY SALES. SOUTH KOREA OUT. TPX IMAGES OF THE DAY A general view shows a Pyongyang city mass rally held at Kim Il Sung Square on August 9, 2017, to fully support the statement of the Democratic People's Republic of Korea (DPRK) government in this photo released on August 10, 2017 by North Korea's Korean Central News Agency (KCNA) in Pyongyang. KCNA/via REUTERS ATTENTION EDITORS - THIS IMAGE WAS PROVIDED BY A THIRD PARTY. REUTERS IS UNABLE TO INDEPENDENTLY VERIFY THIS IMAGE. NO THIRD PARTY SALES. SOUTH KOREA OUT. NO COMMERCIAL OR EDITORIAL SALES IN SOUTH KOREA.?? A general view shows a Pyongyang city mass rally held at Kim Il Sung Square on August 9, 2017, to fully support the statement of the Democratic People's Republic of Korea (DPRK) government in this photo released on August 10, 2017 by North Korea's Korean Central News Agency (KCNA) in Pyongyang. KCNA/via REUTERS ATTENTION EDITORS - THIS IMAGE WAS PROVIDED BY A THIRD PARTY. REUTERS IS UNABLE TO INDEPENDENTLY VERIFY THIS IMAGE. NO THIRD PARTY SALES. SOUTH KOREA OUT. NO COMMERCIAL OR EDITORIAL SALES IN SOUTH KOREA.?? People participate in a Pyongyang city mass rally held at Kim Il Sung Square on August 9, 2017, to fully support the statement of the Democratic People's Republic of Korea (DPRK) government in this photo released on August 10, 2017 by North Korea's Korean Central News Agency (KCNA) in Pyongyang. KCNA/via REUTERS ATTENTION EDITORS - THIS IMAGE WAS PROVIDED BY A THIRD PARTY. REUTERS IS UNABLE TO INDEPENDENTLY VERIFY THIS IMAGE. NO THIRD PARTY SALES. SOUTH KOREA OUT. NO COMMERCIAL OR EDITORIAL SALES IN SOUTH KOREA.? People participate in a Pyongyang city mass rally held at Kim Il Sung Square on August 9, 2017, to fully support the statement of the Democratic People's Republic of Korea (DPRK) government in this photo released on August 10, 2017 by North Korea's Korean Central News Agency (KCNA) in Pyongyang. KCNA/via REUTERS ATTENTION EDITORS - THIS IMAGE WAS PROVIDED BY A THIRD PARTY. REUTERS IS UNABLE TO INDEPENDENTLY VERIFY THIS IMAGE. NO THIRD PARTY SALES. SOUTH KOREA OUT. NO COMMERCIAL OR EDITORIAL SALES IN SOUTH KOREA.? A general view shows a Pyongyang city mass rally held at Kim Il Sung Square on August 9, 2017, to fully support the statement of the Democratic People's Republic of Korea (DPRK) government in this photo released on August 10, 2017 by North Korea's Korean Central News Agency (KCNA) in Pyongyang. KCNA/via REUTERS ATTENTION EDITORS - THIS IMAGE WAS PROVIDED BY A THIRD PARTY. REUTERS IS UNABLE TO INDEPENDENTLY VERIFY THIS IMAGE. NO THIRD PARTY SALES. SOUTH KOREA OUT. NO COMMERCIAL OR EDITORIAL SALES IN SOUTH KOREA. A view shows a Pyongyang city mass rally held at Kim Il Sung Square on August 9, 2017, to fully support the statement of the Democratic People's Republic of Korea (DPRK) government in this photo released on August 10, 2017 by North Korea's Korean Central News Agency (KCNA) in Pyongyang. KCNA/via REUTERS ATTENTION EDITORS - THIS IMAGE WAS PROVIDED BY A THIRD PARTY. REUTERS IS UNABLE TO INDEPENDENTLY VERIFY THIS IMAGE. NO THIRD PARTY SALES. SOUTH KOREA OUT. NO COMMERCIAL OR EDITORIAL SALES IN SOUTH KOREA.? A view shows a Pyongyang city mass rally held at Kim Il Sung Square on August 9, 2017, to fully support the statement of the Democratic People's Republic of Korea (DPRK) government in this photo released on August 10, 2017 by North Korea's Korean Central News Agency (KCNA) in Pyongyang. KCNA/via REUTERS ATTENTION EDITORS - THIS IMAGE WAS PROVIDED BY A THIRD PARTY. REUTERS IS UNABLE TO INDEPENDENTLY VERIFY THIS IMAGE. NO THIRD PARTY SALES. SOUTH KOREA OUT. NO COMMERCIAL OR EDITORIAL SALES IN SOUTH KOREA.? TOPSHOT - This picture taken on August 11, 2017 and released by North Korea's official Korean Central News Agency (KCNA) on August 12, 2017 shows North Korean youths and workers and trade union members holding a rally to protest the UN Security Council's 'sanctions resolution' at the compound of the Monument to Party Founding in Pyongyang. Nearly a week ago, the UN Security Council unanimously passed fresh sanctions against Pyongyang over its weapons program, including export bans, a new punishment that could cost North Korea $1 billion a year. / AFP PHOTO / KCNA VIS KNS AND AFP PHOTO / STR / South Korea OUT / REPUBLIC OF KOREA OUT ---EDITORS NOTE--- RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT 'AFP PHOTO/KCNA VIA KNS' - NO MARKETING NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS THIS PICTURE WAS MADE AVAILABLE BY A THIRD PARTY. AFP CAN NOT INDEPENDENTLY VERIFY THE AUTHENTICITY, LOCATION, DATE AND CONTENT OF THIS IMAGE. THIS PHOTO IS DISTRIBUTED EXACTLY AS RECEIVED BY AFP. / (Photo credit should read STR/AFP/Getty Images) This picture taken on August 11, 2017 and released by North Korea's official Korean Central News Agency (KCNA) on August 12, 2017 shows North Korean youths and workers and trade union members holding a rally to protest the UN Security Council's 'sanctions resolution' at the Youth Park Open-Air theatre in Pyongyang. Nearly a week ago, the UN Security Council unanimously passed fresh sanctions against Pyongyang over its weapons program, including export bans, a new punishment that could cost North Korea $1 billion a year. / AFP PHOTO / KCNA VIS KNS AND AFP PHOTO / STR / South Korea OUT / REPUBLIC OF KOREA OUT ---EDITORS NOTE--- RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT 'AFP PHOTO/KCNA VIA KNS' - NO MARKETING NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS THIS PICTURE WAS MADE AVAILABLE BY A THIRD PARTY. AFP CAN NOT INDEPENDENTLY VERIFY THE AUTHENTICITY, LOCATION, DATE AND CONTENT OF THIS IMAGE. THIS PHOTO IS DISTRIBUTED EXACTLY AS RECEIVED BY AFP. / (Photo credit should read STR/AFP/Getty Images) A view shows a Pyongyang city mass rally held at Kim Il Sung Square on August 9, 2017, to fully support the statement of the Democratic People's Republic of Korea (DPRK) government in this photo released on August 10, 2017 by North Korea's Korean Central News Agency (KCNA) in Pyongyang. KCNA/via REUTERS ATTENTION EDITORS - THIS IMAGE WAS PROVIDED BY A THIRD PARTY. REUTERS IS UNABLE TO INDEPENDENTLY VERIFY THIS IMAGE. NO THIRD PARTY SALES. SOUTH KOREA OUT. NO COMMERCIAL OR EDITORIAL SALES IN SOUTH KOREA.? This picture taken on August 10, 2017 and released by North Korea's official Korean Central News Agency (KCNA) on August 11, 2017 shows service personnel of the Ministry of People's Security at a rally in support of North Korea's stance against the US, in Pyongyang. / AFP PHOTO / KCNA VIA KNS / STR / South Korea OUT / REPUBLIC OF KOREA OUT ---EDITORS NOTE--- RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT 'AFP PHOTO/KCNA VIA KNS' - NO MARKETING NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS THIS PICTURE WAS MADE AVAILABLE BY A THIRD PARTY. AFP CAN NOT INDEPENDENTLY VERIFY THE AUTHENTICITY, LOCATION, DATE AND CONTENT OF THIS IMAGE. THIS PHOTO IS DISTRIBUTED EXACTLY AS RECEIVED BY AFP. / (Photo credit should read STR/AFP/Getty Images) A view shows a Pyongyang city mass rally held at Kim Il Sung Square on August 9, 2017, to fully support the statement of the Democratic People's Republic of Korea (DPRK) government in this photo released on August 10, 2017 by North Korea's Korean Central News Agency (KCNA) in Pyongyang. KCNA/via REUTERS ATTENTION EDITORS - THIS IMAGE WAS PROVIDED BY A THIRD PARTY. REUTERS IS UNABLE TO INDEPENDENTLY VERIFY THIS IMAGE. NO THIRD PARTY SALES. SOUTH KOREA OUT. NO COMMERCIAL OR EDITORIAL SALES IN SOUTH KOREA.? This picture taken on August 10, 2017 and released by North Korea's official Korean Central News Agency (KCNA) on August 11, 2017 shows service personnel of the Ministry of People's Security at a rally in support of North Korea's stance against the US, in Pyongyang. / AFP PHOTO / KCNA VIA KNS / STR / South Korea OUT / REPUBLIC OF KOREA OUT ---EDITORS NOTE--- RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT 'AFP PHOTO/KCNA VIA KNS' - NO MARKETING NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS THIS PICTURE WAS MADE AVAILABLE BY A THIRD PARTY. AFP CAN NOT INDEPENDENTLY VERIFY THE AUTHENTICITY, LOCATION, DATE AND CONTENT OF THIS IMAGE. THIS PHOTO IS DISTRIBUTED EXACTLY AS RECEIVED BY AFP. / (Photo credit should read STR/AFP/Getty Images) A general view shows a Pyongyang city mass rally held at Kim Il Sung Square on August 9, 2017, to fully support the statement of the Democratic People's Republic of Korea (DPRK) government in this photo released on August 10, 2017 by North Korea's Korean Central News Agency (KCNA) in Pyongyang. KCNA/via REUTERS ATTENTION EDITORS - THIS IMAGE WAS PROVIDED BY A THIRD PARTY. REUTERS IS UNABLE TO INDEPENDENTLY VERIFY THIS IMAGE. NO THIRD PARTY SALES. SOUTH KOREA OUT. NO COMMERCIAL OR EDITORIAL SALES IN SOUTH KOREA.?? Up Next See Gallery Discover More Like This HIDE CAPTION SHOW CAPTION of SEE ALL BACK TO SLIDE

“The chance that North Korea might provide jihadis with some of their chemical or nuclear capability is a huge concern at the moment,” he said. “What some people forget ... is that in 2006 North Korea helped [Syrian President Bashar al-] Assad and his regime set up their own nuclear program which was destroyed by the Israelis. But only as recently as a few weeks ago, the Organization for the Prohibition of Chemical Weapons intercepted two North Korean ships heading towards northern Syria with equipment to make chemical weapons.”

De Bretton-Gordon has described VX as "the most toxic chemical weapon ever produced," highlighting that even a "microscopic amount" can prove deadly. VX also featured in the 1996 action thriller "The Rock."

It's banned under several international conventions and was designated a weapon of mass destruction by a U.N. resolution in April 1991. Its origins date back to the early 1950s, when a British scientist named Ranajit Ghosh was researching pesticides and developed the "V-series" of nerve agents — the V stood for "venom."

De Bretton-Gordon, who now works for military supplier Avon, fears impoverished Pyongyang could be more tempted to sell its chemical stockpile as it grapples with toughening global sanctions.

"We know that the jihadis have a lot of money and only last year tried to buy a highly enriched uranium from Russian criminals for $40 million a kilogram," he said. "So, would Kim Jong Un sell deadly VX for $40 million a kilogram? I think absolutely they would the more that they get pushed."

However, Professor Hazel Smith at London's School of Oriental and African Studies (SOAS) says that would be a major change in policy for the North Korean regime.

RELATED: North Korea's Missiles

15 PHOTOS North Korea's Missiles See Gallery North Korea's Missiles The scene of the intermediate-range ballistic missile Pukguksong-2's launch test in this undated photo released by North Korea's Korean Central News Agency (KCNA) May 22, 2017. KCNA/via REUTERS ATTENTION EDITORS - THIS IMAGE WAS PROVIDED BY A THIRD PARTY. EDITORIAL USE ONLY. REUTERS IS UNABLE TO INDEPENDENTLY VERIFY THIS IMAGE. NO THIRD PARTY SALES. SOUTH KOREA OUT. The long-range strategic ballistic rocket Hwasong-12 (Mars-12) is launched during a test in this undated photo released by North Korea's Korean Central News Agency (KCNA) on May 15, 2017. KCNA via REUTERS REUTERS ATTENTION EDITORS - THIS IMAGE WAS PROVIDED BY A THIRD PARTY. EDITORIAL USE ONLY. REUTERS IS UNABLE TO INDEPENDENTLY VERIFY THIS IMAGE. NO THIRD PARTY SALES. SOUTH KOREA OUT. Missiles are driven past the stand with North Korean leader Kim Jong Un and other high ranking officials during a military parade marking the 105th birth anniversary of North Korea's founding father, Kim Il Sung, in Pyongyang, April 15, 2017. REUTERS/Sue-Lin Wong North Korean leader Kim Jong Un inspects the long-range strategic ballistic rocket Hwasong-12 (Mars-12) in this undated photo released by North Korea's Korean Central News Agency (KCNA) on May 15, 2017. KCNA via REUTERS REUTERS ATTENTION EDITORS - THIS IMAGE WAS PROVIDED BY A THIRD PARTY. EDITORIAL USE ONLY. REUTERS IS UNABLE TO INDEPENDENTLY VERIFY THIS IMAGE. NO THIRD PARTY SALES. SOUTH KOREA OUT. TPX IMAGES OF THE DAY People cheer as a missile is driven past the stand with North Korean leader Kim Jong Un and other high ranking officials during a military parade marking the 105th birth anniversary of country's founding father Kim Il Sung, in Pyongyang April 15, 2017. REUTERS/Damir Sagolj Military vehicles carry missiles with characters reading 'Pukkuksong' during a military parade marking the 105th birth anniversary of country's founding father, Kim Il Sung in Pyongyang, April 15, 2017. REUTERS/Damir Sagolj TPX IMAGES OF THE DAY North Korean leader Kim Jong Un supervised a ballistic rocket launching drill of Hwasong artillery units of the Strategic Force of the KPA on the spot in this undated photo released by North Korea's Korean Central News Agency (KCNA) in Pyongyang March 7, 2017. KCNA/via REUTERSATTENTION EDITORS - THIS PICTURE WAS PROVIDED BY A THIRD PARTY. REUTERS IS UNABLE TO INDEPENDENTLY VERIFY THE AUTHENTICITY, CONTENT, LOCATION OR DATE OF THIS IMAGE. FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. NO THIRD PARTY SALES. NOT FOR USE BY REUTERS THIRD PARTY DISTRIBUTORS. SOUTH KOREA OUT. NO COMMERCIAL OR EDITORIAL SALES IN SOUTH KOREA. TPX IMAGES OF THE DAY A fire drill of ballistic rockets by Hwasong artillery units of the KPA Strategic Force is pictured in this undated photo released by North Korea's Korean Central News Agency (KCNA) in Pyongyang September 6, 2016. KCNA/via Reuters ATTENTION EDITORS - THIS PICTURE WAS PROVIDED BY A THIRD PARTY. REUTERS IS UNABLE TO INDEPENDENTLY VERIFY THE AUTHENTICITY, CONTENT, LOCATION OR DATE OF THIS IMAGE. FOR EDITORIAL USE ONLY. NO THIRD PARTY SALES. SOUTH KOREA OUT. THIS PICTURE IS DISTRIBUTED EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS. FILE PHOTO - An underwater test-firing of a strategic submarine ballistic missile is seen in this undated photo released by North Korea's Korean Central News Agency (KCNA) in Pyongyang on April 24, 2016. KCNA/File Photo via REUTERS. ATTENTION EDITORS - THIS IMAGE WAS PROVIDED BY A THIRD PARTY. EDITORIAL USE ONLY. REUTERS IS UNABLE TO INDEPENDENTLY VERIFY THIS IMAGE. SOUTH KOREA OUT. A view of a firing contest among multiple launch rocket system (MLRS) batteries selected from large combined units of the KPA, in this undated photo released by North Korea's Korean Central News Agency (KCNA) in Pyongyang on December 21, 2016. KCNA/via Reuters ATTENTION EDITORS - THIS PICTURE WAS PROVIDED BY A THIRD PARTY. REUTERS IS UNABLE TO INDEPENDENTLY VERIFY THE AUTHENTICITY, CONTENT, LOCATION OR DATE OF THIS IMAGE. FOR EDITORIAL USE ONLY. NO THIRD PARTY SALES. SOUTH KOREA OUT. THIS PICTURE IS DISTRIBUTED EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS. Ballistic rocket is seen launching during a drill by the Hwasong artillery units of the KPA Strategic Force in this undated picture provided by KCNA in Pyongyang on July 21, 2016. KCNA/via ReutersATTENTION EDITORS - THIS IMAGE WAS PROVIDED BY A THIRD PARTY. EDITORIAL USE ONLY. REUTERS IS UNABLE TO INDEPENDENTLY VERIFY THIS IMAGE. SOUTH KOREA OUT. NO THIRD PARTY SALES. NOT FOR USE BY REUTERS THIRD PARTY DISTRIBUTORS.Ã TPX IMAGES OF THE DAY A test launch of ground-to-ground medium long-range ballistic rocket Hwasong-10 in this undated photo released by North Korea's Korean Central News Agency (KCNA) on June 23, 2016. REUTERS/KCNA ATTENTION EDITORS - THIS PICTURE WAS PROVIDED BY A THIRD PARTY. REUTERS IS UNABLE TO INDEPENDENTLY VERIFY THE AUTHENTICITY, CONTENT, LOCATION OR DATE OF THIS IMAGE. FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. NO THIRD PARTY SALES. NOT FOR USE BY REUTERS THIRD PARTY DISTRIBUTORS. SOUTH KOREA OUT. NO COMMERCIAL OR EDITORIAL SALES IN SOUTH KOREA. THIS PICTURE IS DISTRIBUTED EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS. TPX IMAGES OF THE DAY A new multiple launch rocket system is test fired in this undated photo released by North Korea's Korean Central News Agency (KCNA) in Pyongyang March 4, 2016. REUTERS/KCNA ATTENTION EDITORS - THIS PICTURE WAS PROVIDED BY A THIRD PARTY. REUTERS IS UNABLE TO INDEPENDENTLY VERIFY THE AUTHENTICITY, CONTENT, LOCATION OR DATE OF THIS IMAGE. FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. THIS PICTURE IS DISTRIBUTED EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS. NO THIRD PARTY SALES. SOUTH KOREA OUT. NO COMMERCIAL OR EDITORIAL SALES IN SOUTH KOREA A rocket is launched during a demonstration of a new large-caliber multiple rocket launching system attended by North Korean leader Kim Jong Un (not pictured) at an unknown location, in this undated file photo released by North Korea's Korean Central News Agency (KCNA) on March 22, 2016. REUTERS/KCNA/Files ATTENTION EDITORS - THIS PICTURE WAS PROVIDED BY A THIRD PARTY. REUTERS IS UNABLE TO INDEPENDENTLY VERIFY THE AUTHENTICITY, CONTENT, LOCATION OR DATE OF THIS IMAGE. FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. NO THIRD PARTY SALES. SOUTH KOREA OUT. NO COMMERCIAL OR EDITORIAL SALES IN SOUTH KOREA. THIS PICTURE IS DISTRIBUTED EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS. TPX IMAGES OF THE DAY A rocket is fired during a drill by anti-aircraft units of the Korean People's Army (KPA) in this undated photo released by North Korea's Korean Central News Agency (KCNA) in Pyongyang November 3, 2015. REUTERS/KCNA ATTENTION EDITORS - THIS PICTURE WAS PROVIDED BY A THIRD PARTY. REUTERS IS UNABLE TO INDEPENDENTLY VERIFY THE AUTHENTICITY, CONTENT, LOCATION OR DATE OF THIS IMAGE. FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. THIS PICTURE IS DISTRIBUTED EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS. NO THIRD PARTY SALES. SOUTH KOREA OUT. NO COMMERCIAL OR EDITORIAL SALES IN SOUTH KOREA. Up Next See Gallery Discover More Like This HIDE CAPTION SHOW CAPTION of SEE ALL BACK TO SLIDE

"Historically North Korea values state sovereignty and doesn't value interactions with non-state entities such as ISIS and al Qaeda," she said. "Given the level of surveillance over their shipping activities it's also unlikely they would be able to, or try to transport weapons."

She says the regime would be more concerned right now with protecting its oil imports, which are still flowing despite economic sanctions.

There also fears that North Korea could put VX to use itself. Japanese Prime Minister Shinzo Abe has warned of that possibility, and Pyongyang's recent successful missile launch tests and nuclear tests have heightened the likelihood of chemical warfare in any conflict on the Korean peninsula.

"I think we now know that they have 5,000 tons of VX," de Bretton-Gordon said, speaking to NBC News at the Defence and Security Equipment International conference in London. "We know they have missiles capable of firing 4,000 to 6,000 miles, probably with a payload of half a ton, so half a ton of VX in those missiles could kill tens of thousands of people, and they could do that now, so that is a genuine concern."

He added: "We are focusing on the nuclear ... but whatever military option there is [for dealing with] North Korea, it must include mitigating and destroying that very large stock of VX that we know of.”

But Smith says chemical weaponry doesn't form part of the regime's strategic plans.

"Were there to be an escalation of the current crisis, there would next be the use of conventional weapons. [North Korea] would not need chemical weapons for an attack on Seoul [and] if it did ... it would invite a wholesale global response to any military conflict between North and South Korea."

North Korea has said in public statements that it wants an official end to the Korean War, which was halted by a 1953 armistice but not ended by peace treaty. It also wants nothing short of full normalization of relations with the U.S. and to be treated with respect and as an equal in the global arena.

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