The plea stemmed from Special Counsel Robert Mueller’s investigation into Russia’s role in the 2016 election and whether the Trump campaign conspired with Moscow to boost his chances, and put new pressure on the president.

Cohen, who in the past described himself as Trump’s “fixer”, entered his guilty plea in federal court in Manhattan to one count of making false statements to two congressional committees about a real estate project Trump was pursuing while running for president in 2016.

Cohen said in court that in 2017 he submitted a written statement to congress saying all efforts relating to the real estate project in Moscow had ceased by January 2016. Cohen said that in fact these efforts continued until June 2016, after Trump had clinched the Republican presidential nomination.

The proposal to build a skyscraper bearing Trump’s name in the Russian capital ultimately did not materialise.

Cohen provided false statements to both the Senate and House intelligence committees to create the false impression the Moscow real estate project had ended by the time the political primary season began, the charging document said.

“He’s a weak person and not a very smart person,” Trump said of Cohen today.

He told reporters: “He’s got himself a big prison sentence. And he’s trying to get a much lesser prison sentence by making up this story.”

Trump, who last week submitted written answers to questions posed in Mueller investigation, called the project a “deal that didn’t happen” mostly because he was busy running for president, but defended its propriety.

“Now here’s the thing. Even if he was right, it doesn’t matter because I was allowed to do whatever I wanted during the campaign. I was running my business, a lot of different things during the campaign,” Trump added.

Cohen said that in his statement to congress, he claimed to have had limited contact with Trump concerning the project, when in fact it had been “more extensive”.

Cohen also said he falsely told congress he never took any steps towards travelling to Russia, when in fact he had discussed travelling there, although he never did.

“I made these misstatements to be consistent with individual 1’s political messaging and out of loyalty to individual 1,” Cohen said in court. He previously identified individual 1 as Trump.

In August, Cohen pleaded guilty to campaign finance violations, tax evasion and bank fraud in a case brought by federal prosecutors in New York.

Mueller, who took over the Russia investigation from the FBI in May 2017, has brought criminal charges against a series of former Trump aides and associates, including his former campaign chairman Paul Manafort and former national security adviser Michael Flynn, as well as Russian individuals and entities.

Cohen has previously said he would “take a bullet” for the president.

Trump has sought to distance himself from Cohen despite their long association.

Cohen testified in August that Trump had directed him to commit a crime by arranging payments to silence two women who alleged before the 2016 election that they had affairs with Trump. Adult-film star Stormy Daniels was given $US130,000 and former Playboy model Karen McDougal was paid $US150,000.

– AAP