Tuesday's report by The New York Times that President Donald Trump asked James B. Comey, then the FBI director, in February to drop the investigation into his former national security adviser, Michael T. Flynn, has fueled accusations that the White House is obstructing justice.
The head of the US House oversight committee, Jason Chaffetz, asked the Federal Bureau of Investigation to hand over all documents about meetings and communications between Mr Comey and President Trump.
And amid the bubbling crises, Trump is set to depart at the end of the week on his first foreign trip as president, traveling to a North Atlantic Treaty Organisation meeting in Brussels, Belgium; a G7 meeting in Italy; Saudi Arabia; the Vatican; and Israel - the country whose intelligence about an ISIS plot to use laptops on airplanes Trump reportedly breached protocol by sharing with the Russians.
Flynn was forced out in February after he misled the vice-president about his conversations with Russia's ambassador before Trump took office.
Comey had written memos to document every meeting and phone call he had with the president, the sources told the Times.
"For example, if the President said to Comey, 'Listen, I'm not telling you what to do, do what you think is right, but I really hope you can let this go on Flynn because I think he's a great guy, ' there's a lot of people who think that would be an inappropriate statement. This is not a truthful or accurate portrayal of the conversation between the president and Mr. Comey", the statement said.
No White House spokesman would make an on-the-record comment in the immediate aftermath of the disclosure.More news: Democrats raise "obstruction of justice" concerns over Comey memo
"It's the longstanding position of the executive branch that the president can not be indicted while in office", said Harvard law professor Jack Goldsmith, a top Justice Department official under President George W. Bush.
Trump has denied that he asked Comey to close the FBI investigation into Flynn.
It wasn't immediately clear who within the FBI received or saw the memo, or whether acting FBI Director Andrew McCabe was among them.
"James Comey better hope that there are no "tapes" of our conversations before he starts leaking to the press!" he wrote. Comey's intent was to document what he perceived to be the president's improper efforts to influence the investigation, the sources said.
TRUMP UNEASE: Traders appear to be growing concerned over the outlook for the Trump administration both politically and economically.
The dollar dropped half a percent in early trade. USA stocks were poised for a lower opening with Dow futures and the broader S&P 500 futures down 0.4 percent.
On Tuesday the Bloomberg dollar spot index slipped to its lowest level since November on reports that the president had revealed sensitive intelligence to Russian officials. Most in Congress, including many Republicans, seemed to hold the view that the Constitution sets up impeachment as the mechanism for punishing presidential misconduct.More news: Iranian presidential nominee criticizes Rouhani over imports from China
Senate foreign relations chairman Robert Corker said on Monday that the White House was "in a downward spiral". But we have an obligation to carry out our oversight regardless of which party is in the White House.
Representative Adam Kinzinger, an Illinois Republican, went further.
"I think the process is going to go quickly". "I think it'd be a fascinating job".
Yeomans, a 26-year veteran at the Department of Justice, added: "The question of whether criminal indictment can precede impeachment has never been addressed by a court - it's an open question".
Nixon resigned office in 1974, engulfed by the Watergate scandal.
"We are witnessing an obstruction of justice case unfolding in real time", Connecticut Sen. "And there's more behind it".More news: China rappers to Seoul: 'Big brother' opposes missile shield
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