Donald Trump. Mark Wilson/Getty Images President Donald Trump told Russian diplomats in an Oval Office meeting last week that his firing of "nut job" FBI Director James Comey had taken "great pressure" off of him, The New York Times reported Friday.

An American official read the comments, from a White House document summarizing the meeting with Russian Foreign Minister Sergey Lavrov and Ambassador to the US Sergey Kislyak, to The Times. White House press secretary Sean Spicer did not dispute the comments.

"I just fired the head of the FBI. He was crazy, a real nut job," Trump said, according to The Times. "I faced great pressure because of Russia. That's taken off.

"I'm not under investigation," he added.

The conversation happened on May 10, a day after Trump fired Comey, who had been overseeing the FBI's investigation into whether Trump campaign operatives colluded with Russian officials to interfere in the 2016 presidential election. At that same meeting, Trump revealed to the Russians highly classified intelligence on ISIS that the US had not even shared with close allies. That intelligence was later reported to have come from Israel.

Speaking to NBC News' Lester Holt on May 11, Trump mentioned the Russia investigation when explaining why he fired Comey, whom he called a "showboat" and a "grandstander."

"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," he said.

Trump also said Comey assured him on three occasions that he was not personally under investigation, including at a January dinner in which Trump reportedly asked Comey to pledge his loyalty to him.

Earlier this week, The Times reported that Comey kept detailed memos of his conversations with Trump, including one from a February meeting in which Trump suggested he "let go" of the investigation into Michael Flynn, the former national security adviser, who had resigned the day before. Legal experts have said the request could constitute obstruction of justice, the charge that led President Richard Nixon to resign.

On Wednesday, Deputy Attorney General Rod Rosenstein appointed a special counsel, former FBI Director Robert Mueller, to oversee the FBI's Russia investigation. Trump on Thursday tweeted that the move was part of "the single greatest witch hunt of a politician in American history!"

The White House document read to The Times was based on notes taken during the meeting. It was circulated as the official account.

"By grandstanding and politicizing the investigation into Russia's actions, James Comey created unnecessary pressure on our ability to engage and negotiate with Russia," Spicer told The Times. "The investigation would have always continued, and obviously, the termination of Comey would not have ended it. Once again, the real story is that our national security has been undermined by the leaking of private and highly classified conversations."

Another government official who spoke to The Times said Trump was using a "negotiating tactic" with Lavrov when he explained the "pressure" he faced.

The Times wrote: "The idea, the official suggested, was to create a sense of obligation with Russian officials and to coax concessions out of Mr. Lavrov — on Syria, Ukraine, and other issues — by saying that Russian meddling in last year's election had created enormous political problems for Mr. Trump."