Longtime Donald Trump lawyer Michael Cohen sat down for breakfast with billionaire Mark Cuban, who hasn't ruled out making his own run for president, to talk about a book and the pressure of federal probes.

The pair indicated that Cohen was getting help with his forthcoming book about the Trump campaign and the Russia probe – but Cuban said he was also there to talk Cohen 'off the roof' while he's under investigation.

Cuban also tangled with federal investigators during a Securities and Exchange Commission probe where he was found not liable for insider trading.

Longtime Donald Trump lawyer Michael Cohen sat down for breakfast with billionaire Mark Cuban Thursday

He says he wanted to 'calm him down and talk him off the roof,' TMZ reported, having snagged a brief interview with the pair as they departed Landmarc restaurant in the Time Warner Center in New York.

Cohen said he was 'cooperating 100 per cent' with special counsel Robert Mueller's Russia probe.

'I have not comment with anything that they're doing. I'll tell you one thing you can end up reading it in my book,' he responded when asked about it.

Cuban wouldn't bite when asked about a pair of potential Democratic candidates. He has previously indicated he might run. 'I don't play that close attention to politics,' he said.

Cohen plugged his forthcoming book about the campaign and the investigation

Marc Cuban and Michael Cohen exit the Landmarc restaurant in New York

Cuban isn't ruling out a run for president. Cohen has been a longtime legal advisor to Donald Trump

'I'm here to help with his book,' he added.

The two men are reportedly longtime friends. Cuban was once a Trump backer, but appeared side-by-side with Hillary Clinton during the campaign after he concluded he supported her.

His wealth is estimated by Forbes at more than $3 billion. Cuban owns the Dallas Mavericks, appears on 'Shark Tank,' and played the president in 'Sharknado 3,' and has said he is developing ideas on health care and other issues.

Cohen features prominently in the 'dirty dossier' that features unsubstantiated allegations about connections between Trump associates and Russians.

His lawyer vigorously disputed the dossier in a letter to the House Intelligence Committee, noting, for example, that he never traveled to Prague, where he was purported to have gone to meet with Russians in August 2016.

'Mr. Cohen vehemently denies the claims made in the dossier about him, which are false and remain wholly unsubstantiated,' attorney Stephen Ryan wrote the panel, NPR reported.

The SEC went after Cuban for alleged insider trading but he was found not guilty by a Jury in 2013.

Cohen met with House Intelligence panel investigators in October, but Senate probers cancelled his closed appearance after he gave a statement to the media, which the committee claimed violated an agreement.

Then the Senate panel scheduled an Oct. 20 open appearance, and Democratic Sen. Mark Warner of Virginia said he 'appreciates Mr. Cohen's cooperation.'