President Donald Trump will deny he ever asked former FBI director James Comey to go easy on fired former national security adviser Michael Flynn if made to testify about it under oath, his lawyer Rudy Giuliani said today.

"There was no conversation about Michael Flynn," Giuliani said on CNN's "State of the Union" show, of the February 14, 2017, Oval Office meeting.

The private sit-down is a key episode in Special Counsel Robert Mueller's investigation into possible obstruction of justice in the Russia election meddling probe.

Comey testified in Congress last year that Trump sought to pressure him to back off on Flynn the day after the president fired his national security adviser for lying about contacts he had had with the Russian ambassador.

"I hope you can see your way to letting Flynn go. He's a good guy. I hope you can let this go," Comey quoted Trump as saying.

Trump fired Comey in May 2017, later admitting the FBI's Russia probe was on his mind at the time.

Trump has previously denied Comey's version of the meeting about Flynn, without going into detail.

But the former FBI director's contemporaneous memos of his interactions with Trump, which were leaked and ultimately made public in redacted form earlier this year, are a central feature of Mueller's inquiry into whether Trump sought to obstruct the Russia probe. And Flynn has since agreed to cooperate with investigators as part of a plea bargain on charges of lying to investigators.

Giuliani said Trump's denial of the "let this go" comment is "what (Trump) will testify to if he's asked that question." He said if Trump were to agree to be interviewed by Mueller and his team in hopes of putting the investigation to rest, questions about his dealings with Comey would be off limit to avoid what his lawyers see as a "possible perjury trap." "If we ever had a trial -- I don't think we will -- if he goes in and testifies to that under oath instead of this being a dispute, they can say it's perjury if they elect to believe Comey, instead of Trump," he said.