By Alexander J Martin, news reporter
The Mueller investigation has found no evidence that Donald Trump's campaign "conspired or coordinated" with Russia to interfere in the 2016 presidential election.
However, the report does not exonerate the president of obstruction of justice, the Justice Department said.
A letter summarising its main findings, sent by the US Attorney General William Barr to members of Congress, said there was not enough evidence to prove charges of obstruction.
Mr Trump welcomed what he described as "complete and total exoneration", adding the inquiry was the result of "an illegal take-down that failed", and saying it was "a shame the country had to go through this".
Mr Trump's supporters also welcomed the finding that there was no collusion.
Lindsay Graham, the Senate judiciary committee chairman, called for the country to "move on" while White House spokeswoman Sarah Sanders also described the findings of the report as a "total and complete exoneration of the president of the United States".
The chairman of the House judiciary committee, Jerry Nadler, said the report "is putting matters squarely in Congress' court".
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Mr Nadler, who is a Democrat, disputed the idea that the president couldn't be prosecuted for obstruction of justice, as the attorney general had assessed.
He said that "in light of the very concerning discrepancies and final decision making [by Mr Barr] following the special counsel report, where Mueller did not exonerate the President, we will be calling Attorney General Barr in to testify".
Special counsel Robert Mueller has spent almost two years examining Russian interference in the 2016 presidential election.
After charging 34 individuals, issuing 2,800 subpoenas and executing almost 500 search warrants, Mr Mueller submitted his report to Mr Barr.
According to Mr Barr, the investigation did not find that the Trump campaign or its associates "conspired or coordinated" with Russia, according to the letter he sent to Congress which summarises Mueller's findings.
Mr Barr also wrote that he "concluded that the evidence developed during the special counsel's investigation is not sufficient to establish that the president committed an obstruction-of-justice offence".
However, he noted that such evidence would need to prove "beyond a reasonable doubt" that the president intended to obstruct justice.
The letter advises Congress of the "principal conclusions" of the investigation, although it remains unclear whether the entire report – which is confidential – will ever be published.
According to Cordelia Lynch, Sky News' US correspondent: "The reality is the public may never learn the full scope of what Mr Mueller and his team have found."
In the letter, Mr Barr said "my goal and intent is to release as much of the special counsel's report as I can" but that this would be limited by the laws and regulations of the department.
By Alexander J Martin, news reporter
The Mueller investigation has found no evidence that Donald Trump's campaign "conspired or coordinated" with Russia to interfere in the 2016 presidential election.
However, the report does not exonerate the president of obstruction of justice, the Justice Department said.
A letter summarising its main findings, sent by the US Attorney General William Barr to members of Congress, said there was not enough evidence to prove charges of obstruction.
Mr Trump welcomed what he described as "complete and total exoneration", adding the inquiry was the result of "an illegal take-down that failed", and saying it was "a shame the country had to go through this".
Mr Trump's supporters also welcomed the finding that there was no collusion.
Lindsay Graham, the Senate judiciary committee chairman, called for the country to "move on" while White House spokeswoman Sarah Sanders also described the findings of the report as a "total and complete exoneration of the president of the United States".
The chairman of the House judiciary committee, Jerry Nadler, said the report "is putting matters squarely in Congress' court".
More from US
Mr Nadler, who is a Democrat, disputed the idea that the president couldn't be prosecuted for obstruction of justice, as the attorney general had assessed.
He said that "in light of the very concerning discrepancies and final decision making [by Mr Barr] following the special counsel report, where Mueller did not exonerate the President, we will be calling Attorney General Barr in to testify".
Special counsel Robert Mueller has spent almost two years examining Russian interference in the 2016 presidential election.
After charging 34 individuals, issuing 2,800 subpoenas and executing almost 500 search warrants, Mr Mueller submitted his report to Mr Barr.
According to Mr Barr, the investigation did not find that the Trump campaign or its associates "conspired or coordinated" with Russia, according to the letter he sent to Congress which summarises Mueller's findings.
Mr Barr also wrote that he "concluded that the evidence developed during the special counsel's investigation is not sufficient to establish that the president committed an obstruction-of-justice offence".
However, he noted that such evidence would need to prove "beyond a reasonable doubt" that the president intended to obstruct justice.
The letter advises Congress of the "principal conclusions" of the investigation, although it remains unclear whether the entire report – which is confidential – will ever be published.
According to Cordelia Lynch, Sky News' US correspondent: "The reality is the public may never learn the full scope of what Mr Mueller and his team have found."
In the letter, Mr Barr said "my goal and intent is to release as much of the special counsel's report as I can" but that this would be limited by the laws and regulations of the department.
