No proof that Trump conspired with Russia: Barr

US Attorney General William Barr has said Special Counsel Robert Mueller did not find proof that Donald Trump or his campaign conspired with Russia to interfere in the 2016 presidential elections, following which the US president claimed "complete and total exoneration".

In his four-page letter to the Congress on Sunday, which was later made public, Barr however said that "while this (Mueller's) report does not conclude that the president committed a crime, it also does not exonerate him" and sets out evidence on "both sides of the question".

The investigation had cast a shadow over the Trump presidency for nearly two years with the Democratic leadership alleging that Russian interference helped him in the 2016 polls.

Barr said that Mueller found no proof of such a conspiracy "despite multiple offers from Russia-affiliated individuals to assist the Trump campaign".

"The special counsel's investigation did not find that the Trump campaign or anyone associated with it conspired or coordinated with Russia in its efforts to influence the 2016 US presidential election," the attorney general said.

Mueller, in his report, "did not draw a conclusion - one way or the other - as to whether the examined conduct constituted obstruction", Barr told the lawmakers.

"For each of the relevant actions investigated, the report sets out evidence on both sides of the question and leaves unresolved what the special counsel views as 'difficult issues' of law and fact concerning whether the president's actions and intent could be viewed as obstruction," Barr said, adding Mueller "ultimately determined not to make a traditional prosecutorial judgment".

In the letter, he also said the Department of Justice has determined that there is not sufficient evidence to establish that Trump committed obstruction of justice.

"After reviewing the special counsel's final report on these issues; consulting with department officials, including the Office of Legal Counsel; and applying the principles of federal prosecution that guide our charging decisions, Deputy Attorney General Rod Rosenstein and I have concluded that the evidence developed during the special counsel's investigation is not sufficient to establish that the President committed an obstruction-of-justice offense," the letter read.

"The special counsel's investigation did not find that the Trump campaign or anyone associated with it conspired or coordinated with Russia in its efforts to influence the 2016 US presidential election," it said, adding, "the report identifies no actions that, in our judgement, constitute obstructive conduct."

The Democrats were banking heavily on the results of the Mueller investigation to defeat Trump in the 2020 elections. Many were also talking about impeaching the president if the report reveals collusion between Russia and the Trump campaign.

"It was complete and total exoneration," the president told reporters in Florida as he was returning from Mar-a-Lago to Washington DC.

Terming the allegation of collusion "the most ridiculous thing ever", Trump said, "It's a shame that our country had to go through this. To be honest, it's a shame that your president had to go through this."

He had been repeatedly claiming that he was a victim of "witch hunt", while asserting that there was no collusion between his campaign and the Russians.

"This was an illegal takedown that failed and hopefully somebody is going to be looking at their other side," Trump said.

"After a long look, after a long investigation, after so many people have been so badly hurt, after not looking at the other side where a lot of bad things happened... it was just announced there was no collusion with Russia," he said, adding "It's a complete exoneration."

White House Press Secretary Sarah Sanders said the report has justified the president's stand.

"The special counsel did not find any collusion and did not find any obstruction. Attorney General Barr and Deputy Attorney General (Rod) Rosenstein further determined there was no obstruction. The findings of the Department of Justice are a total and complete exoneration of the President of the United States," she said.

Republican National Committee chairwoman Ronna McDaniel said this is a great day for all Americans.

"As we have said all along, there was no collusion and no obstruction. Now that this investigation is over, Democrats need to finally end their baseless investigations and political crusade against President Trump for the good of the country," she said.

Trump's campaign manager Brad Parscale said the president has been "completely and fully vindicated" by Mueller's report.

"After issuing 2,800 subpoenas and 500 search warrants, interviewing 500 witnesses, employing 40 FBI agents and 19 lawyers, and spending tens of millions of taxpayer dollars, Robert Mueller concluded unequivocally, 'the investigation did not establish that members of the Trump Campaign conspired or coordinated with the Russian government in its election interference activities.' Moreover, the attorney general and the deputy attorney general determined that there was no evidence of obstruction of justice," Parscale said.

"Nevertheless, Democrats took us on a frantic, chaotic, conspiracy-laden roller coaster for two years, alleging wrongdoing where there was none," he claimed.

"So distraught and blindsided by the results of the 2016 elections, Democrats lied to the American people continually, hoping to undo the legitimate election of President Trump," Parscale said.