Donald Trump claimed North Korea was blowing up four of its big missile test sites and has “already started” a process of “total denuclearisation.”

However, officials said there was no evidence to back up the US president’s claims.

On Thursday, Ms Trump told a cabinet meeting in the White House: ”They’ve stopped the sending of missiles, including ballistic missiles. They’re destroying their engine site.

“They’re blowing it up. They’ve already blown up one of their big test sites, in fact it’s actually four of their big test sites.

“And the big thing is it will be a total denuclearisation, which has already started taking place.”

It was not immediately clear which North Korean test sites Mr Trump was referring to, and US officials familiar with current intelligence of North Korea’s nuclear and missile test sites said there was no evidence of new moves to dismantle any sites since Mr Trump met the North Korean leader, Kim Jong-un, on 12 June.

The officials, speaking on condition of anonymity, speculated Mr Trump might have been referring to explosions last month North Korea claimed were the destruction of tunnels at the Punggye-ri nuclear test site and the dismantling of a medium-range ballistic missile test stand at Iha-ri, in May.

There had been contact with North Korean officials since the summit, the US State Department said.

The US secretary of state, Mike Pompeo, “will be meeting with them and talking with them at the earliest possible date” to implement what was agreed in Singapore, a Department of State spokeswoman, Heather Nauert told reporters, without providing further details.

Asked on Wednesday if North Korea had done anything towards denuclearisation since the summit, the US defence secretary, Jim Mattis, told reporters: “No, I’m not aware of that ... obviously, it’s the very front end of a process.

“The detailed negotiations have not begun. I wouldn’t expect that at this point.”

Mr Mattis sat next to Mr Trump at Thursday’s cabinet meeting.

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

The Pentagon did not immediately respond to a request for comment on Mr Trump’s latest remarks. There was also no immediate response from the White House.

The US-based North Korea monitoring group, 38 North, said in an analysis at the end of last week there had been no sign of any activity towards dismantling of any missile test site.

Mr Trump, who has been leading an international drive to press North Korea to abandon development of nuclear missiles capable of reaching the United States, told reporters after the 12 June summit the North’s leader had pledged to dismantle one of his missile installations.

A US official said on Wednesday the site Mr Trump referred to was the Sohae Satellite Launching Ground, a major facility in the western part of the country which has been used for testing engines for long-range missiles.

North Korea announced before the Singapore summit the suspension of its ICBM testing and also closed its nuclear bomb test site, where it conducted several explosions in front of visiting media it said were to destroy testing tunnels.

However, US officials have cautioned such actions are reversible.

In the cabinet meeting, Mr Trump acknowledged “things can change.”

“Personalities can change. Maybe you end up with conflict. Maybe you don’t,” he said.

He said both he and Mr Pompeo had established a “very strong” relationship with the North’s leader he thought would lead to “tremendous success.”

Mr Trump went on to say the “number-one statement” in the document he and Mr Kim signed in Singapore was “we will immediately begin total denuclearisation of North Korea,” although there was no such statement in the text.

In the joint statement, Mr Kim ”reaffirmed his firm and unwavering commitment to complete denuclearisation of the Korean Peninsula,” but made no reference to a timeline.

Going into the summit, Pyongyang repeatedly rejected unilateral nuclear disarmament.

Mr Pompeo told the same cabinet meeting Mr Kim had made a personal commitment, and added: “He has got his reputation on the line.”

Mr Pompeo said US allies and North Korea‘s neighbour and ally China were supportive of the US policy of maintaining sanctions on Pyongyang until its denuclearisation was complete.

Mr Trump repeated his thanks to the Chinese president, Xi Jinping, for supporting sanctions, although he said the border between China and North Korea was “getting a little weaker now.”

“That’s OK. That’s OK. But we have to get him to keep it tough,” Mr Trump said.

Mr Trump also said the remains of US troops missing from the Korean War were in the process of being returned to the United States from North Korea, correcting a statement he made a day earlier.

On Wednesday, Mr Trump said the remains of 200 American servicemen had already been sent back, following the agreement he reached with Mr Kim in Singapore.

Two US officials, speaking on condition of anonymity, said while North Korea was expected to return the remains of soldiers in coming days, they had not yet been returned.