Trump on Thursday lashed out at the appointment of a special counsel to investigate allegations that his campaign collaborated with Russian Federation to sway the 2016 election, tweeting that it was "the single greatest witch hunt of a politician in American history!"
Trump met with the Russians on May 10, the day after he fired Comey.
The FBI's investigation has bedeviled the Trump administration, and the president personally. A Washington Post report, citing anonymous sources familiar with the matter, said a senior Trump adviser is now considered a "person of interest" in the law enforcement investigation into whether Trump's campaign associates coordinated with Russian Federation in an effort to sway the 2016 election.
The news of a potential cover-up investigation came just hours after the Washington Post reported that an official now working in the Trump administration who is close to the president is a "significant person of interest" in the investigation.
The White House has disputed Comey's account of his February conversation with Trump concerning Flynn but has not offered specifics. Trump has denied any collusion.
Comey will testify in an open committee session sometime after Memorial Day, the senators said in the statement on Friday, although no date has yet been set.
In a potential bombshell, the Washington Post reports that investigators are focusing on a current White House official close to Trump as a person of interest in their probe into the administration's ties to Russian Federation.
Separately the New York Times reported that Trump boasted to Russian officials at a White House meeting last week that firing Comey relieved "great pressure" the president faced from a law-enforcement probe into Russian meddling in the 2016 election. "He was insane, a real nut job", Trump said, according to the Times.More news: Ousted FBI chief to brief senators in public hearing
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"There is no reason he can't testify before both the Intelligence and Judiciary Committees, particularly given that the Judiciary Committee is the FBI's primary oversight committee", Judiciary Committee Chairman Charles Grassley, R-Iowa, and ranking Democrat Dianne Feinstein, D-Calif., wrote in a statement.
"The investigation would have always continued, and obviously, the termination of Comey would not have ended it", Spicer said, adding that the real story was the leaks of "private and highly classified conversations".
A United States official briefed on the conversation said Trump was using "pressure" he faced from Comey as a negotiating ploy to win diplomatic gains from Lavrov on issues of dispute between Washington and Moscow - namely Syria and Ukraine.
In response to the latest reports on Friday, White House Press Secretary Sean Spicer again rejected the allegations and said, "A thorough investigation will confirm that there was no collusion between the campaign and any foreign entity". "I faced great pressure because of Russian Federation".
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.
The Justice Department on Wednesday appointed former FBI director Robert Mueller to lead the investigation.
The Justice Department on Friday released the text of Rosenstein's opening remarks for the briefings on Capitol Hill.
She said it's a "ridiculous statement" for Trump to make and results in "elevating the Russians as his confidante at the expense of our justice system".