North Korea has threatened to push ahead with its nuclear weapons programme if the US does not lift “foolish” sanctions against the country.

The regime’s foreign ministry issued the warning as Mike Pompeo, US secretary of state, indicated economic pressure would be maintained until leader Kim Jong-un followed through on his commitment to denuclearisation.

The war of words follows months of diplomatic wrangling over how to move forward from the June summit between Donald Trump and the North Korean leader.

The statement, issued in the name of the director of the foreign ministry’s Institute for American Studies, claimed “the improvement of relations and sanctions is incompatible”.

“The US thinks that its oft repeated ‘sanctions and pressure’ leads to ‘denuclearisation’ – we cannot help laughing at such a foolish idea,” it said.

“If the US keeps behaving arrogantly without showing any change in its stand, while failing to properly understand our repeated demand, the DPRK [Democratic People’s Republic of Korea] may add one thing to the state policy for directing all efforts to the economic construction adopted in April, and as a result the word ‘pyongjin’ may appear again.”

Pyongjin, or “dual advancement”, refers to the policy of strengthening both the North Korean economy and its nuclear force.

In April Kim Jong-un said the policy had achieved a “great victory” and had allowed the country to shift its focus solely to economic development.

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North Korea has since declared a suspension of nuclear and long-range missile tests, as well as the dismantling of its nuclear testing ground, although experts were not invited to observe the event.

Describing those steps as “proactive and goodwill measures”, the foreign ministry suggested that the US should lift sanctions before further nuclear talks.

Their statement marked the first time the North said it could potentially resume weapons tests and other development activities.

North Korea military parade celebrating nation's 70th anniversary Show all 18 1 /18 North Korea military parade celebrating nation's 70th anniversary North Korea military parade celebrating nation's 70th anniversary Participants wave flowers AFP/Getty North Korea military parade celebrating nation's 70th anniversary North Korea's leader Kim Jong Un (R) waves with China's Chairman of the Standing Committee of the National People's Congress Li Zhanshu (L) from a balcony AFP/Getty North Korea military parade celebrating nation's 70th anniversary Airplanes forming the number 70 fly in formation and fire flares AP North Korea military parade celebrating nation's 70th anniversary North Korean performers dance EPA North Korea military parade celebrating nation's 70th anniversary North Korean military officers applaud near portraits of late North Korean leaders Kim Il Sung and Kim Jong Il AP North Korea military parade celebrating nation's 70th anniversary North Korean tanks roll past AP North Korea military parade celebrating nation's 70th anniversary Participants cheer as they take part in a parade for the 70th anniversary of North Korea's founding day in Pyongyang, North Korea, Sunday, Sept. 9, 2018. North Korea staged a major military parade, huge rallies and will revive its iconic mass games on Sunday to mark its 70th anniversary as a nation. (AP Photo/Ng Han Guan) Ng Han Guan AP North Korea military parade celebrating nation's 70th anniversary Korean People's Army (KPA) soldiers take part AFP/Getty North Korea military parade celebrating nation's 70th anniversary Korean People's Army (KPA) soldiers march AFP/Getty North Korea military parade celebrating nation's 70th anniversary Participants march during a mass rally on Kim Il Sung square in Pyongyang AFP/Getty North Korea military parade celebrating nation's 70th anniversary A girl reacts during a parade AP North Korea military parade celebrating nation's 70th anniversary North Korean leader Kim Jong Un, right, reacts as he chats with China's third highest ranking official, Li Zhanshu AP North Korea military parade celebrating nation's 70th anniversary People carry flags in front of statues of North Korea founder Kim Il Sung (L) and late leader Kim Jong Il Reuters North Korea military parade celebrating nation's 70th anniversary Performers take part in a concert at the Pyongyang Indoor Stadium AFP/Getty North Korea military parade celebrating nation's 70th anniversary North Korean artillery roll past AP North Korea military parade celebrating nation's 70th anniversary Students perform Reuters North Korea military parade celebrating nation's 70th anniversary Soldiers march during a military parade Reuters North Korea military parade celebrating nation's 70th anniversary Participants wave flowers AFP/Getty

Mr Pompeo, in an interview with Fox News on Friday, said he planned to talk with his North Korean counterpart next week.

“A lot of work remains, but I’m confident that we will keep the economic pressure in place until such time as Chairman Kim fulfills the commitment he made to President Trump back in June in Singapore,” he said.

No location or date for the meeting was given but it is thought the secretary of state will focus on persuading North Korea to take firmer steps towards denuclearisation and preparations for a second summit.

In September the US president said he expected to meet Kim Jong-un again “in the immediate future”.

Protesters tear up a US flag during a rally in front of the embassy in Seoul, South Korea (AP)

Growing concern that North Korea is dragging its feet over denuclearisation led South Korea to drop its proposal to lift some of its unilateral sanctions last month, after Mr Trump warned that South Korea could “do nothing” without US approval.

Demonstrators gathered in South Korea on Saturday to oppose further talks between the US and North Korea (AP)

On Saturday rival protest groups gathered near the US embassy in Seoul, South Korea. One supported the US policy of keeping pressure on North Korea while the other opposed it.