After earlier reports had indicated that Trump asked former FBI Director James Comey to close the agency's investigation into former national security adviser Michael Flynn, some lawmakers and legal experts said if the reports are true, Trump may have committed obstruction of justice, an impeachable offense.
President Trump refrained from tweeting about so-called witch hunts and "phony" stories on Wednesday, June 14, when Mr. Trump spoke at the White House about the attacks of 66-year-old James T. Hodgkinson of Belleville, Illinois, against congressmen and Capitol Police in Alexandria, Virginia.
In a series of statements on Twitter Thursday, Trump repeated his assertion that Mueller's investigation into Russian interference in the 2016 campaign is a "WITCH HUNT" based on the "phony" premise of possible collusion between Russia and a cadre of Trump campaign associates. Since then, Mueller, who served as FBI director before Comey, took over the investigation.
Senior US intelligence officials have agreed to be interviewed by investigators working for Robert Mueller, a respected former Federal Bureau of Investigation chief, according to reports in both The Washington Post and New York Times.
Obstruction of justice is a potentially impeachable offense.
The Post referred to anonymous sources who had been briefed on requests made by Mueller's investigators.
He reiterated tweets from Thursday morning about the investigation.
Mr Comey testified under oath that Mr Trump had told him during a private meeting: "I hope you can see your way clear to letting this go, to letting Flynn go". "Why is that Hillary Clintons family and Dems dealings with Russian Federation are not looked at, but my non-dealings are?", Trump tweeted just before 4 p.m. EDT.
Supporters of Trump condemned the news leaks regarding the new investigation.
Rosenstein told a closed session of Congress last month that he learned Comey would be dismissed one day before penning his memo.
Trump has consistently denied any collusion between himself or any of his associates and Russian Federation.
"The Vice-President is focused entirely on his duties and promoting the President's agenda and looks forward to a swift conclusion of this matter", a Pence spokesman said.
The White House has denied any collusion, and Trump has repeatedly complained about the probe, saying Democrats can not accept his election win. That committee is also reviewing Russian election meddling and any ties to the Trump campaign.