WASHINGTON — The F.B.I. director, James B. Comey, took the extraordinary step on Monday of announcing that the F.B.I. is investigating whether members of President Trump’s campaign colluded with Russia to influence the 2016 election.
Mr. Comey’s remarks before the House Intelligence Committee created a treacherous political moment for Mr. Trump, who has insisted that “Russia is fake news” that was cooked up by his political opponents to undermine his presidency. Mr. Comey placed a criminal investigation at the doorstep of the White House and said agents would pursue it “no matter how long that takes.”
Mr. Comey also dismissed Mr. Trump’s claim that he was wiretapped by his predecessor during the campaign, a sensational but unfounded accusation that has served as a distraction in the public debate over Russian election interference.
The New York Times and other news organizations have reported the existence of the investigation into the Trump campaign and its relationship with Russia, but the White House dismissed those reports as politically motivated and rallied political allies to rebut them. Mr. Comey’s testimony on Monday was the first public acknowledgment of the case. The F.B.I. typically discloses its investigations only in the rare circumstances when officials believe it is in the public interest.
“This is one of those circumstances,” Mr. Comey said.
Counterintelligence investigations are among the F.B.I.’s most difficult and time-consuming cases, meaning the cloud of a federal investigation could hang over the Trump administration for years.