US President Donald Trump has raised the possibility that a congressional hearing Democrats arranged with his former personal lawyer may have contributed to the lack of results of his summit with North Korean leader Kim Jong Un.

Mr Trump left the summit in Vietnam with the North Korean leader last week without reaching an agreement.

After sending out national security adviser John Bolton to the Sunday talk shows to describe the summit as a success, Mr Trump showed his frustration about the results by lashing out at Democrats.

In a tweet on Sunday night, Mr Trump criticised Democrats for holding the congressional hearing with Michael Cohen while he was in sensitive negotiations overseas.

“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.” Never done when a president is overseas. Shame!” Mr Trump tweeted.

As Mr Trump wrapped up his trip to the summit last week, he complained about why Democrats had to hold the hearing at the same time as his negotiations.

He described it as a “fake hearing” and said having it in the middle of this “very important summit” was “really a terrible thing”.

Mr Trump said they could have held it a few days later and had more time to prepare.

During the House Oversight Committee hearing, Mr Cohen was harshly critical of his former boss, calling him a racist, con man and a cheat.

Mr Bolton earlier on Sunday described the summit as a success despite the lack of an agreement providing for verifiable dismantling of the North’s nuclear sites.

Mr Bolton, in three television interviews, tried to make the case that Mr Trump advanced America’s national security interests by rejecting a bad agreement while working to persuade Mr Kim to take “the big deal that really could make a difference for North Korea”.

The US and North Korea have offered contradictory accounts of why last week’s summit in Vietnam broke down, though both pointed to American sanctions as a sticking point.

In news show appearances, Mr Bolton said the leaders left on good terms and that Mr Trump made an important point to North Korea and other countries that negotiate with him.

“He’s not desperate for a deal, not with North Korea, not with anybody if it’s contrary to American national interests,” Mr Bolton said.