Mr Mueller also investigated whether Mr Trump obstructed justice but did not come to a definitive answer, Attorney General William Barr said in a letter to Congress summarising Mr Mueller’s report.
The special counsel “does not exonerate” Mr Trump of obstructing justice, Mr Barr said, and his report “sets out evidence on both sides of the question”.
After consulting with other Justice Department officials, Mr Barr said he and Deputy Attorney General Rod Rosenstein determined the evidence “is not sufficient to establish that the president committed an obstruction of justice offence”.
Mr Barr released a four-page summary of Mr Mueller’s report on Sunday afternoon. Mr Mueller wrapped up his investigation on Friday with no new indictments, bringing to a close a probe that has shadowed Mr Trump for nearly two years.
Mr Barr’s chief of staff called White House counsel Emmet Flood on Sunday to brief him on the report to Congress. Mr Trump was at his Mar-a-Lago resort in Florida, about to return to Washington after spending the weekend there.
White House press secretary Sarah Sanders tweeted that Mr Trump had been completely exonerated.
Senate Judiciary Committee chairman Lindsey Graham added that “the cloud hanging over President Trump has been removed”.
Mr Graham, a close ally of Mr Trump, also said it is “a bad day for those hoping the Mueller investigation would take President Trump down”.
Republican Doug Collins said “there is no constitutional crisis” while House Majority Leader Kevin McCarthy, also a Republican said “it is time we move on for the good of the nation”.
Eric Trump, the President’s son, called for a “simple apology” from the media for “the hell everyone has been put through” during the two-year probe.
But the House Judiciary Committee chairman said Mr Mueller “clearly and explicitly is not exonerating the president”.
Democrat Jerry Nadler tweeted that Mr Barr’s letter to Congress says that while Mr Trump may have acted to obstruct justice, the government would need to prove that “beyond a reasonable doubt”.
But Mr Nadler tweeted that Congress must hear from Mr Barr about his decision making and see “all the underlying evidence for the American people to know all the facts”.
Mr Mueller’s investigation ensnared nearly three dozen people, senior Trump campaign operatives among them.
The probe illuminated Russia’s assault on the American political system, painted the Trump campaign as eager to exploit the release of hacked Democratic emails to hurt Democrat Hillary Clinton and exposed lies by Trump aides aimed at covering up their Russia-related contacts.
Mr Mueller submitted his report to Mr Barr instead of directly to Congress and the public because, unlike independent counsels such as Ken Starr in the case of President Bill Clinton, his investigation operated under the close supervision of the Justice Department, which appointed him.
Mr Mueller was assigned to the job in May 2017 by Mr Rosenstein, who oversaw much of his work.
Mr Barr and Mr Rosenstein analysed Mr Mueller’s report on Saturday, labouring to condense it into a summary letter of main conclusions.