"I was wrong," Comey said in an interview with Fox News Sunday.
Lawyers for McCabe, who has not yet been charged in the case, met last month with a top Justice official in what were believed to be talks seeking to dissuade officials from filing criminal charges.
Comey is not being prosecuted for the alleged violations detailed in the scathing report by the DOJ's Office of Inspector General.
Trump's attempts to affect the Russia probe mostly failed because the people around him "declined to carry out orders," according to Robert Mueller's team.
The Mueller report says evidence obtained about Trump's "actions and intent" makes it difficult to determine whether a crime occurred.
The nearly 400-page report represents the culmination of 22 months of investigation by Mueller's team, although the fight over the probe isn't likely to end when the redacted document is released.
Rosenstein tells The Wall Street Journal that Attorney General William Barr is "being as forthcoming as he can."
Former FBI Director James Comey told NBC News on Wednesday he views his 2017 firing by President Donald Trump as "potentially obstruction of justice."
As Democrats digest the Mueller report's findings, House Speaker Nancy Pelosi must decide how to proceed, without letting politics get in the way.
The handoff marks the long-anticipated end of the high-profile and highly guarded Russia probe, nearly two years after it began.
"It's frustrating to me, but I can't imagine the country being any different," Comey said.
In a Washington spectacle unseen since the wife of Richard Nixon's attorney general sounded alarms about Watergate, the spouse of a top presidential advisor is issuing urgent public warnings about Trump's mental health, writes CNBC's John Harwood.
Comey said that he did not know if Democrats could obtain an unredacted copy of the Mueller report with a subpoena if the Department of Justice declined to release it.
The attorney general will not recuse himself from oversight of the special counsel investigation, a Justice Department spokeswoman said.
The Republican former governor of New Jersey says he wants to help the president, but he's content to do it from afar.
McCabe tells NBC he had informed congressional leaders that the FBI had opened a counterintelligence probe into Trump after the firing of James Comey, and that none of the members objected to it.
Rod Rosenstein, the U.S. deputy attorney general who appointed special counsel Robert Mueller to investigate possible ties between Russia and President Donald Trump's campaign, is expected to step down by mid March.
President Donald Trump's firing of FBI Director James Comey led to the appointment of special counsel Robert Mueller, who is investigating whether Trump's presidential campaign colluded with Russian interference in the 2016 election.
Former FBI Deputy Director Andrew McCabe said he spoke with Trump in May 2017, just after the president fired ex-FBI Director James Comey.
Schiller was hired by the RNC to help select a site for the 2020 convention. But once Charlotte, North Carolina, was announced in July, Schiller's firm was kept on to "work on other security needs for the committee," a party official told CNBC.