WASHINGTON (Reuters) - U.S. President Donald Trump sought to backtrack on comments last year in which he tied his decision to fire FBI Director James Comey to a probe into Russian election meddling, accusing NBC News on Thursday of “fudging” their interview, but offering no supporting evidence.

Trump made his accusation as the man who took over the federal Russia investigation from Comey, Special Counsel Robert Mueller, digs deeper into a probe that has already led to a series of indictments of former Trump aides.

Trump fired Comey on May 9, 2017, a move that Comey said later was aimed at undercutting the probe.

The Trump administration said at the time of Comey’s dismissal that the president had acted on the recommendation of Attorney General Jeff Sessions and No. 2 Justice Department official Rod Rosenstein.

In an interview with NBC Nightly News anchor Lester Holt that aired two days after the firing, Trump accused Comey of being incompetent and noted the recommendation, but also raised the issue of the Russia investigation, saying he was thinking of “this Russia thing” when he fired him.

In a Twitter post on Thursday, Trump accused the news outlet and Holt, of “fudging my tape on Russia,” but gave no evidence to back up his claim.

In addition to looking into Russia’s alleged interference in the 2016 presidential election, which Moscow denies, Mueller is investigating any collusion with Russia by Trump’s campaign and any attempt by the president to impede the probe.

The Comey firing could be central to a potential obstruction of justice case. Legal experts have said Mueller’s team must weigh whether the president acted with an improper, or “corrupt,” intent when he took actions such as firing Comey.

Trump has denied any collusion with Russia, or any obstruction of justice. He has said since the interview with Holt that he did not fire Comey over the federal probe.

U.S. President Donald Trump answers questions from the news media during an event at which he announced a grant for a drug-free communities support program in the Roosevelt Room of the White House in Washington, U.S., August 29, 2018. REUTERS/Leah Millis

Trump said in the Holt interview, “regardless of recommendation, I was going to fire Comey knowing there was no good time to do it And in fact, when I decided to just do it, I said to myself — I said, you know, this Russia thing with Trump and Russia is a made-up story. It’s an excuse by the Democrats for having lost an election that they should’ve won.”

Representatives for NBC News, part of Comcast Corp CMCSA.O, declined to comment on Trump's tweets on Thursday.

Representatives for the White House did not respond to a question about Trump’s accusation.

ATTACKS ON NEWS MEDIA

In the most dramatic day yet in the Russia investigation, federal prosecutors last week secured the conviction of Trump’s former campaign manager for financial crimes and a plea agreement from the president’s longtime attorney that included pleading guilty to campaign finance violations.

Trump, in a string of tweets last week, said he had nothing to hide from Mueller’s probe.

Trump’s tweets on Thursday were his latest attack on the news media. He has repeatedly called critical reports about him “fake news” and on Thursday he also called for the firing of CNN’s president, Jeff Zucker.

Representatives for CNN, owned by AT&T T.N, declined to comment.

U.S. news organizations have pushed back against the stream of criticism from Trump.

Federal authorities on Thursday charged a California man with threatening to kill Boston Globe employees for the newspaper’s role leading a defense this month of press freedoms by hundreds of news organizations.

Shares of AT&T and Comcast did not move on the president’s tweets.