The completion of the special counsel's investigation marks the end of one of the most dramatic chapters in Donald Trump's presidency, one that led to numerous criminal charges against and guilty pleas by some of his closest associates.
Guessing when Mueller's report will be turned over to the Department of Justice has become a popular Washington parlour game, though the special counsel has not officially indicated that his probe is in its final stages.
In a letter to lawmakers, Mr Barr said Mr Mueller had concluded the probe, that he is reviewing the report and will be consulting the deputy attorney general and Mr Mueller to determine what information from it can be released to Congress.
Special Counsel Robert Mueller's investigation into alleged collusion between Russian Federation and President Donald Trump's 2016 campaign has concluded.
In appointing Danforth, Attorney General Janet Reno specifically directed him to draft a report for public release on his findings, which he did.
In an op-ed for The New York Times published Friday, former FBI Director James Comey lays out "what I want from the Mueller report". He has repeatedly claimed that the entire Mueller investigation was a "witch hunt", and recently tweeted that he believed there should be "no Mueller report" at all. On Feb. 22, six Democratic committee chairs with the broadest oversight powers wrote a letter to Barr requesting they receive the report "without delay and to the maximum extent permitted by law".
What exactly was Mueller investigating again? .
The president said that Mr Mueller was "best friend" to Mr Comey.
The report is meant to explain any prosecutorial decisions the special counsel has made in the 22 months since his appointment by deputy US Attorney General Rod Rosenstein. The special counsel's findings on the question of obstruction of justice are also unknown, but Trump's allies will likely argue anything short of a criminal indictment proves the President did nothing wrong. "I'm also not rooting for Mr. Mueller to "clear" the president".
Democrats control the House and some already have pledged to subpoena the report and Mueller and go to court if necessary to secure its full release.
One week before Mueller's appointment, Trump fired FBI Director James Comey, later saying he was thinking of "this Russian Federation thing" at the time. "It's all a big hoax".