Trump thanks Kim Jong-un for ‘nice letter’ following reports North Korea is developing new missile

'I am not at all surprised that you took this kind action,' president tweets

North Korean leader Kim Jong-un shakes hands with US President Donald Trump during their historic US-DPRK summit (Getty)

US president Donald Trump has thanked North Korean leader Kim Jong-un for his “nice letter” and “kind action”, just days after US intelligence agencies reported signs that the North was constructing new a ballistic missile.

Mr Trump tweeted his thanks to Mr Kim for returning select remains from the Korean War some 65 years after the conflict ended. The remains were transported to the US in 55 flag-draped coffins on Wednesday, and were received by Vice President Mike Pence.

“Thank you to Chairman Kim Jong Un for keeping your word & starting the process of sending home the remains of our great and beloved missing fallen!” Mr Trump tweeted on Wednesday night. “I am not at all surprised that you took this kind action.”

He added: “Also, thank you for your nice letter - l look forward to seeing you soon!”

White House Press Secretary Sarah Huckabee Sanders said in a statement that the “ongoing correspondence” between the two leaders was aimed at “following up” on their meeting in Singapore and “advancing the commitments made in the US-DPRK joint statement”.

The White House did not comment on whether Mr Trump and Mr Kim would meet again.

The two leaders’ meeting in June resulted in a vaguely-worded statement, in which Mr Kim agreed to "work towards complete denuclearisation of the Korean Peninsula" but provided few concrete promises towards achieving that goal.

Mr Trump has since halted joint military drills with South Korea, and the North appears to have shut down its nuclear test site and started dismantling its rocket launch site.

Earlier this week, however, the Washington Post reported that US intelligence agencies had received evidence that North Korea was constructing at least one liquid-fuelled intercontinental ballistic missile. The construction was reportedly taking place at the same factory that produced the country’s first missile capable of reaching the US.

Officials familiar with the intelligence, told the Post that senior North Korean officials had also discussed plans to deceive the US about the number of nuclear warheads, missiles, and facilities they possessed, as well as plans to rebuff international inspectors.

Secretary of State Mike Pompeo acknowledged last week that North Korean factories continued to produce materials used in making nuclear weapons, despite the Singapore agreement.

Asked whether Pyongyang’s nuclear programme was advancing on the whole, Mr Pompeo declined to answer, saying public statements on the matter would not be helpful in negotiations with a “difficult adversary”.

"I'm not trying to be cute,” the secretary said at a Senate hearing. “We're engaged in a complex negotiation with a difficult adversary, and each of the activities that we undertake is not going to be fully apparent to the world at the moment it is undertaken."