"I just fired the head of the FBI He was insane, a real nut job", Trump said, according to official meeting notes which were read aloud to the New York Times by an administration source.
The White House press secretary, Sean Spicer, said in a statement on Friday that "by grandstanding and politicizing the investigation into Russia's actions, James Comey created unnecessary pressure on our ability to engage and negotiate with Russian Federation".
Since Comey was abruptly fired by Donald Trump, reports have surfaced suggesting a tense relationship between the former Federal Bureau of Investigation director and the president.
Law enforcement officials now consider a senior Trump adviser a "person of interest" in the probe, the Post reported, citing people familiar with the matter.
The summary was drawn from a formal account of last week's meeting between Mr Trump, Russian Foreign Minister Sergei Lavrov and the Russian Ambassador Sergei Kislyak, who is at the centre of numerous controversial contacts between the Trump campaign and senior Russian officials. "He was insane, a real nutjob", the newspaper reported, referring to a summary of the conversation.
Comey, who was leading an FBI investigation into Trump's campaign team and whether it colluded with the Kremlin during the 2016 election, was sacked earlier this month.
"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 said.
Trump on Thursday slapped down the accusations against him and said he was the victim of the "greatest witch hunt" in American political history.
The White House has struggled since Comey's firing to explain the chain of events that led to it and who exactly made the decision.
He says his memo is not a finding of official misconduct and is not a statement of reasons to justify Comey's firing.
He then told the pair, "I'm not under investigation".
Rosenstein said in testimony to the Congress this week that investigators are now looking into the possibility of a coverup by the White House, unidentified lawmakers told McClatchy Friday. The remaining 6 percent had "mixed feelings."U.S. stocks immediately pared gains after the reports but still closed higher for a second straight day.Earlier this week, investors dumped stocks in response to reports that Trump in February had asked Comey to stop investigating his former national security adviser, prompting accusations the president may have tried to hamper the probe".
She said subjects of the investigation could later argue that its results cannot be trusted, but she believes the argument would not stand up in court.
Rosenstein denied media reports from last week that Comey had asked him for additional resources for his investigation before Trump fired him.