Mr. Trump denied the account, but it was not clear whether he was genuinely revealing the existence of clandestine recordings or simply making a rhetorical point that Mr. Comey’s version of events was false.
Mr. Trump chose not to clarify when asked later in the day by Fox News if there were tapes of conversations. “That I can’t talk about. I won’t talk about it,” he said. “All I want is for Comey to be honest.”
No president in the past 40 years has been known to regularly tape his phone calls or meetings because, among other reasons, the recordings could be subpoenaed by investigators as they were during the Watergate investigation that ultimately forced President Richard M. Nixon to resign. Phone calls with foreign leaders are typically transcribed with the knowledge of other participants.
Democrats were incredulous. “For a president who baselessly accused his predecessor of illegally wiretapping him, that Mr. Trump would suggest that he, himself, may have engaged in such conduct is staggering,” said Representative Adam B. Schiff of California, the top Democrat on the House Intelligence Committee.
Representatives John Conyers Jr. of Michigan and Elijah E. Cummings of Maryland, the top Democrats on the judiciary and oversight committees, sent a letter to the White House demanding copies of any recordings if they exist. The letter noted that “it is a crime to intimidate or threaten any potential witness with the intent to influence, delay or prevent their official testimony.”
Asked if the president records his conversations, Sean Spicer, the White House press secretary, would not say. “The president has nothing further to add on that,” Mr. Spicer said, repeating the answer or some variation of it several times as reporters pressed.
He denied that the president was threatening Mr. Comey. “That’s not a threat,” Mr. Spicer said. “He simply stated a fact. The tweet speaks for itself. I’m moving on.”
Mr. Comey made no comment, but later in the day he declined a request to testify before the Senate Intelligence Committee on Tuesday. According to a close associate of Mr. Comey, he is willing to testify, but wants it to be in public.
The matter arose in a series of early-morning Twitter messages in which Mr. Trump appeared agitated over news reports on contradictory accounts of his decision to fire Mr. Comey, which came at the same time the F.B.I. is investigating ties between Mr. Trump’s associates and Russia. Among other things, he threatened to cancel future White House briefings.
The White House’s original version of the story was that the president had acted on the recommendation of the attorney general and deputy attorney general and fired Mr. Comey because of his handling of last year’s investigation into Hillary Clinton’s emails. But in an interview with NBC News on Thursday, Mr. Trump said he had already decided to fire Mr. Comey and would have done so regardless of any recommendation. He also indicated that he was thinking about the Russia investigation when he decided.
Implicitly acknowledging that misinformation had been given out, Mr. Trump said Friday that no one should expect his White House to give completely accurate information.
“As a very active President with lots of things happening, it is not possible for my surrogates to stand at podium with perfect accuracy!” he wrote on Twitter.
“Maybe,” he added a few moments later, “the best thing to do would be to cancel all future ‘press briefings’ and hand out written responses for the sake of accuracy???”
The threat may have been just a jab — Friday’s briefing went forward as scheduled — but Mr. Trump later told Fox that he was thinking about it. “Unless I have them every two weeks and I do them myself, we don’t have them,” he said. “I think it’s a good idea.”
Jeff Mason, a White House correspondent for Reuters and the president of the White House Correspondents’ Association, objected. “Doing away with briefings would reduce accountability, transparency and the opportunity for Americans to see that, in the U.S. system, no political figure is above being questioned,” he said.
There is precedent for shutting down news briefings during Mr. Trump’s presidency. The State Department for decades held daily briefings with only rare and brief interruptions, but such briefings have largely ended during the Trump administration.
Allies and former employees of Mr. Trump have long said that he taped some of his own phone calls, as well as meetings in Trump Tower. During the campaign, Mr. Trump’s aides told reporters that they feared their offices were bugged and that they were careful about what they said.
But the implicit threat to Mr. Comey was ripped from a familiar playbook that Mr. Trump relied on during the campaign to silence critics or dissent.
He threatened on Twitter to tell stories about Joe Scarborough and Mika Brzezinski, the hosts of “Morning Joe” on MSNBC, after they criticized him. He threatened to air unspecified dirty laundry about the wealthy Ricketts family as it financed efforts against him. And competing with Senator Ted Cruz of Texas for the Republican nomination, he threatened to “spill the beans on your wife!”
In this case, however, the warning came in the context of an F.B.I. investigation. Samuel W. Buell, a Duke University law professor and former federal prosecutor who led the Enron task force, said Mr. Trump’s attempt on Twitter to quiet Mr. Comey could be viewed as an effort to intimidate a witness to any future investigation into whether the firing amounted to obstruction of justice.
“If this were an actual criminal investigation — in other words, if there were a prosecutor and a defense lawyer in the picture — this would draw a severe phone call to counsel warning that the defendant is at serious risk of indictment if he continues to speak to witnesses,” Mr. Buell said. “Thus, this is also definitive evidence that Trump is not listening to counsel and perhaps not even talking to counsel. Unprecedented in the modern presidency.”
Mr. Trump’s mention of tapes did nothing to dispel the echoes of Watergate heard in Washington this week. The dismissal of Mr. Comey in the midst of an investigation into Mr. Trump’s associates struck many as similar to Nixon’s decision in October 1973 to fire Archibald Cox, the Watergate special prosecutor who demanded secret White House tapes, in an episode that came to be known as the Saturday Night Massacre.
The difference, according to Luke A. Nichter, a historian at Texas A&M University who has specialized in the tapes, is that “Nixon’s rantings were done in private,” and he did not cancel news briefings. “The reason I have a hard time with the label Nixonian is that we’ve surpassed it,” Mr. Nichter said. “To be Trumpian is something of a greater magnitude than simply being Nixonian.”
Mr. Trump’s defenders have said that Watergate comparisons are overwrought and that there is no evidence of collusion between Mr. Trump’s campaign and Russia during last year’s election. The president has called the suspicions “fake news” concocted by sore-loser Democrats looking to explain a defeat.
“Again, the story that there was collusion between the Russians & Trump campaign was fabricated by Dems as an excuse for losing the election,” he wrote on Twitter on Friday.