Michael Cohen, U.S. President Donald Trump's former longtime personal lawyer, pleaded guilty on Thursday to lying to Congress about a proposed Trump Organization skyscraper in Moscow, prompting the president to lash out at Cohen as a liar and “weak person.”

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

Cohen, a former member of Trump's inner circle who in the past called himself the president's “fixer,” described efforts to pursue Trump's ambitious Moscow real estate project deep into the 2016 U.S. presidential campaign, later than previously disclosed.

He entered his guilty plea in federal court in Manhattan to one count of making false statements to two congressional panels about the project. According to a court document, Cohen briefed Trump on the project more than three times, as well as members of his family.

Not long after Cohen entered his plea, Trump abruptly canceled a meeting with Russian President Vladimir Putin scheduled to take place during this week's Group of 20 industrialized nations summit in Argentina, citing the current Ukraine crisis.

Cohen had pleaded guilty in August to eight criminal charges, including tax evasion, bank fraud and campaign finance violations, in a separate case brought by federal prosecutors in New York. His sentencing in that case is scheduled for December 12.

Cohen said in court on Thursday 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 those efforts continued until June 2016, after Trump had clinched the Republican presidential nomination.

The proposal to build a tower bearing Trump's name in the Russian capital ultimately did not materialize. Cohen provided false statements to both the Senate and House intelligence committees to create the impression the project had ended by the time the political primary season began, the charging document said.

Trump on Thursday distanced himself from Cohen, who last year told an interviewer he would “take a bullet” for the president.

“He's a weak person and not a very smart person,” Trump said to 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's investigation, called the Moscow project a “deal that didn't happen” mostly because he was busy running for president, but defended its propriety.

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

“Everybody knows about this deal. I wasn't trying to hide anything.”

Trump lawyer Rudy Giuliani said the president had provided written answers to questions from Mueller on the Moscow project. Asked whether there was anything in those answers that contradicted Cohen on the project, Giuliani told Reuters: “Not that I know of.”

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 traveling to Russia when in fact he had discussed going there, although he never went.