The president suggested the House of Representatives Oversight Committee’s decision to interview his longtime fixer on the same day he met Kim Jong-un in Hanoi had been a factor in the two leaders’ failure to strike a deal.

He gave no explanation for how Mr Cohen’s testimony could have impacted on negotiations over Pyongyang’s nuclear programme.

Mr Trump tweeted on Sunday night: “For the Democrats to interview in open hearings a convicted liar & fraudster, at the same time as the very important Nuclear Summit with North Korea, is perhaps a new low in American politics and may have contributed to the ‘walk.’

He added: “Never done when a president is overseas. Shame!”

Trump and Kim: leaders arrive in Vietnam for talks Show all 7 1 /7 Trump and Kim: leaders arrive in Vietnam for talks Trump and Kim: leaders arrive in Vietnam for talks Donald Trump and Vietnamese President Nguyen Phu Trong make their way to a meeting at the Presidential Palace in Hanoi Reuters Trump and Kim: leaders arrive in Vietnam for talks Donald Trump waves a Vietnamese flag as Vietnam's Prime Minister Nguyen Xuan Phuc looks on AFP/Getty Trump and Kim: leaders arrive in Vietnam for talks Donald Trump waves as he leaves the Presidential Palace in Hanoi AFP/Getty Trump and Kim: leaders arrive in Vietnam for talks North Korean leader Kim Jong-un, right, is welcomed on his arrival at the Melia Hotel in Hanoi AP Trump and Kim: leaders arrive in Vietnam for talks Kim Jong-un waves as he arrives by train in the Vietnamese border town of Dong Dang AP Trump and Kim: leaders arrive in Vietnam for talks North Korean leader Kim Jong-un receiving a situation report before the summit with Trump AFP/Getty Trump and Kim: leaders arrive in Vietnam for talks The motorcade carrying U.S President Donald Trump drives past Ho Chi Minh Mausoleum AP

The president abruptly ended Thursday’s talks with Mr Kim, telling the media the North Korean leader had demanded “sanctions lifted in their entirety” in exchange for denuclearisation. He said in a subsequent press conference: "Sometimes you have to walk."

Hours earlier, Mr Cohen gave explosive public testimony in which he branded Mr Trump a “racist” and a “conman” who was involved in “criminal conspiracy”.

Asked about his former personal lawyer’s evidence at a press conference in Hanoi on Thursday, the president called the allegations “incorrect” and criticised the decision to hold the hearing while he was away.

“I tried to watch as much as I could,” Mr Trump said. “I wasn’t able to watch too much because I’ve been a little bit busy, but I think having a fake hearing like that and having it in the middle of this very important summit is really a terrible thing.”

Mr Cohen had originally been scheduled to testify to the committee on 7 February but cancelled his appearance, citing “threats against his family” he alleged had been made by Mr Trump and his lawyer Rudy Giuliani. The committee confirmed on 20 February that it had rescheduled the testimony for last week.

The president announced the date of his summit with Mr Kim on 5 February.

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Republican senator Lindsey Graham last week accused Democrats of "undercutting an important foreign policy effort" by holding Mr Cohen's hearing on the same day as the North Korea talks.

North Korea has disputed Mr Trump's explanation for the breakdown of negotiations, saying it wanted only a partial lifting of sanctions in exchange for the dismantlement of its main nuclear facility.