North Korea appears to have begun dismantling a site used to develop components for ballistic missiles, in what would be an important first step towards fulfilling the agreement made at a summit between Donald Trump and Kim Jong-un in June.

Satellite images published by a leading think-tank on North Korea show activity at the Sohae Satellite Launching Station, located among dense forest and hills close the northern border with China.

Workers are believed to be dismantling a building used to assemble space-launch vehicles and a nearby rocket engine test stand used to develop liquid-fuel engines for ballistic missiles and space-launch vehicles, the 38 North think-tank said.

North Korea's weapons programme was high on the agenda at a summit between Mr Trump and Mr Kim in Singapore last month. The US president later said his counterpart had promised to destroy a major missile engine testing site "very soon".

Mr Trump did not identify the site, but a US official subsequently told the Reuters news agency that it was Sohae.

"Since these facilities are believed to have played an important role in the development of technologies for the North’s intercontinental ballistic missile program, these efforts represent a significant confidence-building measure on the part of North Korea," 38 North said in a report.

The apparent progress comes amid concerns over whether North Korea would follow through with the commitments made in Singapore. The White House reportedly admitted that a subsequent trip made by Mike Pompeo to Pyongyang went "as bad as it could have".

US officials have repeatedly said North Korea has committed to giving up a nuclear weapons programme that now threatens the US, but Pyongyang has offered no details as to how it might go about this.

Satellite image from Airbus Defense and Space and 38 North, shows the apparent dismantling of facilities at the Sohae satellite launching station, North Korea (AFP/Getty ) (AFP/Getty)

Jenny Town, managing editor of 38 North, which is based at Washington's Stimson Centre, said the work at Sohae could be an important move to keep negotiations going.

"This could (and that’s a big could) mean that North Korea is also willing to forgo satellite launches for the time being as well as nuclear and missile tests. This distinction has derailed diplomacy in the past," she said.

Singapore Summit: historic first meeting between Trump and Kim Jong-un Show all 20 1 /20 Singapore Summit: historic first meeting between Trump and Kim Jong-un Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump and Mr Kim leave following their historic meeting AFP/Getty Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump and Mr Kim sign a document committing to peace between their nations, amongst other things EPA Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump holds up a document that both he and Mr Kim have signed AFP/Getty Singapore Summit: historic first meeting between Trump and Kim Jong-un The two leaders reach out to shake hands for the first time AP Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump and Mr Kim shake hands as they meet for the first time Reuters Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump and Mr Kim walk off stage, following their historic meeting Reuters Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump and Mr Kim take a stroll after their meeting on June 12 Reuters Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump and Mr Kim interrupt their stroll to talk to the media AP Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Kim and Mr Trump look out over a balcony at the Capella hotel, where they held their meeting on June 12 Reuters Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump takes questions at the press conference following his meeting with with Mr Kim AP Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump appreciates the crowd in the press conference following his meeting with Mr Kim Getty Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump travels to the Istana ahead of the summit with Kim Jong Un on June 12 Reuters Singapore Summit: historic first meeting between Trump and Kim Jong-un Kim Jong Un travels to the Istana ahead of the summit with President Trump on June 12 Reuters Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Kim poses for a photo with Singapore's Finance Minister Vivian Balkrishnan and Education Minister Ong Ye Kung ahead of the summit with Mr Trump Twitter/Reuters Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump shakes hands with Singapore Prime Minister Lee Hsien Loong, meeting on Monday June 11 in the Istana, Singapore's presidential palace AP Singapore Summit: historic first meeting between Trump and Kim Jong-un At a working lunch on Monday, Singapore's Prime Minister surprised Mr Trump with a birthday cake, in early celebration of his 72nd birthday later in the week EPA Singapore Summit: historic first meeting between Trump and Kim Jong-un US Secretary of State Mike Pompeo answers questions about the summit at a press briefing in Singapore on Monday, June 11 Getty Singapore Summit: historic first meeting between Trump and Kim Jong-un US President Donald Trump arrives at the Paya Lebar Air Base in Singapore on June 10, two days prior to his summit with North Korean leader Kim Jong Un Reuters Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump and Mr Kim met on Tuesday June 12 in the Capella hotel on the island resort of Sentosa, just off the south coast of Singapore AFP/Getty Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump boards Air Force One following the summit AFP/Getty

On Friday, senior US officials called on Mr Kim to act on his promise to give up his nuclear weapons and said the world, including China and Russia, must continue to enforce sanctions on Pyongyang until he does so.

And on Monday, the US State Department issued an advisory together with the departments of Treasury and Homeland Security alerting businesses to North Korea's sanctions-evasion tactics.

It said they should "implement effective due diligence policies, procedures, and internal controls to ensure compliance with applicable legal requirements across their entire supply chains."

In a tweet early on Monday, Mr Trump rejected "Fake News" that he was angry because progress was not happening fast enough with North Korea.

"Wrong, very happy!" he said in the Tweet.

"A Rocket has not been launched by North Korea in 9 months. Likewise, no Nuclear Tests. Japan is happy, all of Asia is happy," he said.

A report in The Washington Post at the weekend said that in spite of positive assessments Trump has given on progress with North Korea, he has vented anger at aides over a lack of immediate progress.

Last week, Mr Trump said there was "no rush" and "no time limit" on denuclearisation negotiations.

US Director of National Intelligence Dan Coats said on Thursday it was technically possible for North Korea to eliminate its nuclear weapons program within a year, but added that it was not likely to happen.