North Korea has reportedly expanded a long-range missile base within its mountainous interior, despite a promise from Donald Trump the country was “no longer a threat”.

Satellite images obtained by CNN allegedly show Pyongyang has continued to maintain and update its Yeongjeo-dong missile base and another site nearby.

US officials have long known about the Yeongjeo-dong base, but images show construction on a new facility seven miles away not previously made public, the US news channel reported.

“Satellite images show that the base remains active. Moreover, in the past year North Korea has significantly expanded a nearby facility that appears to be another missile base,” the Middlebury Institute of International Studies at Monterey (MIISM) said in a report seen by CNN.

The images reportedly suggest the large underground facility was being built in 2017 and workers were continuing construction as of August this year.

In June, Mr Trump claimed the world could “now feel much safer” following his summit in Singapore with North Korean dictator Kim Jong-un.

The historic meeting saw the two leaders agree to produce a framework for denuclearisation, though there appears to be considerable difference between the two countries as to what exactly that entails.

“There is no longer a Nuclear Threat from North Korea,” the president tweeted at the time. “Meeting with Kim Jong-un was an interesting and very positive experience. North Korea has great potential for the future!”

North Korea destroys 10 guard posts to lower tensions

In September, he also told supporters at a rally in West Virginia he and Mr Kim were “in love”.

The alleged expansion of an existing missile base comes after MIISM reported in July that satellite images showed North Korea was expanding an important factory for producing solid-fuel motors for its nuclear-armed missiles.

But US intelligence officials have long believed Pyongyang will not denuclearise and will instead look to hide and move nuclear assets.

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Mr Kim would not appear be violating any agreement with the US by continuing to deploy the North’s existing missiles, but the revelation of a missile base under construction comes amid accusations by the Trump administration Pyongyang is failing to live up to its end of the deal.

“They have not lived up to the commitments so far," national security adviser John Bolton said at a conference last month, adding Mr Trump was looking for a second meeting with the North Korean leader.

In November, North Korea cancelled a meeting between its officials and US secretary of state Mike Pompeo, a week after vowing to strengthen its nuclear weapons programme unless America lifted sanctions against them.