President Donald Trump, in an exclusive interview Thursday with NBC News' Lester Holt, called ousted FBI chief James Comey a "showboat" and revealed he asked Comey whether he was under investigation for alleged ties to Russia.

"I actually asked him" if I was under investigation, Trump said, noting that he spoke with Comey once over dinner and twice by phone.

"I said, if it's possible would you let me know, 'Am I under investigation?' He said, 'You are not under investigation.'"

"I know I'm not under investigation," Trump told Holt during the White House interview.

It would be highly unusual for someone who might be the focus of an FBI probe to ask whether he was under investigation and to be directly told by the FBI director that he was not.

Trump also reiterated his claim that he had been planning to fire Comey even before he received Deputy Attorney General Rod Rosenstein's recommendation.

"He's a showboat, he's grandstander, the FBI has been in turmoil," Trump said of Comey in his wide-ranging interview with Holt. "You know that, I know that. Everybody knows that. You take a look at the FBI a year ago, it was in virtual turmoil, less than a year ago. It hasn't recovered from that."

Trump said he never tried to pressure Comey into dropping the FBI probe of the Trump campaign and insisted, "I want to find out if there was a problem in the election having to do with Russia."

Asked by Holt if by firing Comey he was trying to send a "lay off" message to his successor, Trump said, "I'm not."

"If Russia did anything, I want to know that," he said.

But Trump also insisted there was no "collusion between me and my campaign and the Russians."

"Also, the Russians did not affect the vote," he said.

Holt's interview with the president came as Washington was still reeling over Trump's firing of Comey on Tuesday.

Trump insisted he canned Comey because "he was not doing a good job" and the White House on Wednesday cited the FBI chief's handling of the Hillary Clinton email investigation as the reason they were firing the veteran G-man.

The Democrats, many of whom believe that Comey's intrusion into the election helped Trump win the presidency, immediately denounced the move and called for the appointment of a special prosecutor as New York Senator Charles Schumer suggested a "cover-up" was underway.

"The timing of Director Comey's dismissal to me and many committee members on both sides of the aisle is especially troubling," Senator Mark Warner, a Virginia Democrat, said Thursday at the opening of a Senate Intelligence Committee hearing.

"He was leading an active counterintelligence investigation into any links between the Trump campaign and the Russian government or its representatives, and whether there was any coordination between the campaign and Russia's efforts to interfere in our election," he said. "We were scheduled to hear directly from Director Comey in open session today."

Earlier, Deputy White House Press Secretary Sarah Huckabee Sanders insisted Trump "had been considering letting Director Comey go since the day he was elected."

And Trump himself tweeted later Wednesday, "Dems have been complaining for months & months about Dir. Comey. Now that he has been fired they PRETEND to be aggrieved. Phony hypocrites!"

But while Senate Majority Leader Mitch McConnell came out in support of the president, several other key Republicans joined the Democrats in questioning the timing of the Comey firing, although they stopped short of joining their call for a special prosecutor.