WASHINGTON - President Donald Trump insisted Thursday that there was ``no collusion'' between his winning campaign and the Russian government, in his first extended remarks since he roiled Washington with his decision to fire FBI Director James Comey.

In an interview with NBC's Lester Holt, Trump slammed Comey as a ``showboat'' attention-seeker who had lost the confidence of the president and the agency he led.

``Look he's a showboat, he's a grandstander, the FBI has been in turmoil,'' Trump said. ``You know that, I know that. Everybody knows that.''

The White House has denied that Comey's firing Tuesday had anything to do with the FBI's continuing investigation into Russia's interference in the U.S. election, including the possible role of Trump campaign aides and associates. Trump has denied any involvement.

``There's no collusion between me and my campaign and the Russians,'' he declared Thursday.

But Trump acknowledged during the interview that he'd considered the potential ramification of his decision on the inquiry.

``When I did this now I said, `I probably, maybe will confuse people, maybe I'll expand that, you know, lengthen the time,' because it should be over with, in my opinion, should have been over with a long time ago, `cause all it is, is an excuse,'' he said.

Trump aides had insisted in the aftermath of Comey's surprise dismissal that the president had gone ahead with the firing based on the recommendations of his deputy attorney general, Rod Rosenstein.

But Trump threw that explanation under the bus.

``Oh I was going to fire regardless of recommendation,'' he told Holt.

``He made a recommendation, he's highly respected, very good guy, very smart guy, the Democrats like him, the Republicans like him, he made a recommendation but regardless of recommendation I was going to fire Comey,'' he said.

As for the investigation, Trump said that Comey had assured him during a dinner and in two subsequent phone calls that he was not personally under investigation.

``I actually asked him,'' Trump recalled. ``I said, `If it's possible would you let me know, am I under investigation?' He said, `You are not under investigation.'''

The president showed no concern that the inquiry could be viewed as interference into an ongoing FBI probe -- or that his conduct could be seen as a warning to Comey's eventual successor to steer clear of questions about the campaign's possible ties to Russia's election meddling.

Trump also told Holt that he has given a letter to Republican Sen. Lindsey Graham saying he has no investments in Russia.

"I am not involved in Russia, " Trump said. "No loans."