Democrats, who have compared the widening scandal to the Watergate break-in and cover-up that brought down Republican former President Richard Nixon in 1974, were quick to pounce on the latest reports.
Burr says the committee wants to hear from Comey on his role in the development of the US intelligence agencies' assessment that Russian Federation interfered in last year's election.
Rosenstein had briefed the full Senate on Thursday at an event that left several key questions unanswered, including what exactly Trump said to Rosenstein when he told him Comey would be fired, and to what degree congressional investigators will maintain access to witnesses and documents given Rosenstein's appointment of Robert Mueller III, a former Federal Bureau of Investigation director, as special counsel. "He was insane, a real nut job", Trump said, according to the document, which was read to The New York Times by a U.S. official.
President Donald Trump told Russian diplomats last week his firing of "nut job" James Comey had eased the pressure on him, even as the FBI's Trump-Russia investigation had moved into the White House, according to reports Friday that pursued the president as he began his maiden foreign trip. "That's taken off", he said.
The Times cited a document summarizing the meeting which it said was provided by a government official.
"I faced great pressure because of Russian Federation".
It did not deny the Times report that Trump was critical of Comey to the Russians the day after he fired him.
Former FBI Director Robert Mueller was named Special Counsel for the Russian Federation investigation on Wednesday. Mueller will have sweeping powers and the authority to prosecute any crimes he uncovers.
The Justice Department on Friday distributed prepared remarks that Rosenstein delivered to Congress in separate briefings. It immediately escalated the legal stakes - and the potential political damage - for a president who has tried to dismiss the matter as partisan witch hunt and a "hoax".
In another Twitter post Thursday, Trump said: "With all of the illegal acts that took place in the Clinton campaign & Obama Administration, there was never a special councel (sic) appointed". He did not provide examples or evidence of any alleged "illegal acts". Trump has insisted at times that the decision was his alone, but he also has pointed - as recently as Thursday - to the "very strong" recommendation from Rosenstein. The Washington Post reported that a senior Trump administration official is now a "person of interest" in the Russian Federation probe.
The White House repeated its assertion that a "thorough investigation will confirm that there was no collusion between the campaign and any foreign entity".
Spicer offered a new explanation for that firing, saying that Trump had been trying to improve relations with Russian Federation - and Comey got in the way.
Pelosi told The Associated Press in an interview Friday that "every day the president gives us more reason to believe that he does not respect the office that he holds".
On Tuesday, a report uncovered evidence that Trump asked Comey in February to end the FBI's probe of former National Security Adviser Michael Flynn, who resigned in February amid revelations that he misled senior White House officials about the nature of his conversations with Russia's ambassador.
Trump has repeatedly slammed the FBI and congressional investigations as a "hoax" and blamed disgruntled officials at intelligence agencies for leaking information related to the probes.