U.S. special counsel Robert Mueller did not find that Donald Trump's campaign conspired or coordinated with Russia to influence the 2016 U.S. presidential election in his favor, according to a summary of Mueller's report released Sunday.

The summary by Attorney General William Barr also said Mueller drew no conclusions about whether Trump obstructed justice in relation to the special counsel's investigation into Moscow's meddling in the election.

Mueller's nearly two-year probe had cast a deep shadow over Trump's presidency, but the findings are likely to give a boost to the Republican president in his 2020 re-election bid.

"It was a complete and total exoneration," Trump told reporters in Florida. "No collusion. No obstruction."

However, Democratic Rep. Jerry Nadler, chairman of the House Judiciary Committee, said Congress needs to hear from Barr about his decision and see "all the underlying evidence."

Mueller "clearly and explicitly is not exonerating the president," Nadler said in a Twitter post.

According to the four-page summary, the report says the "investigation did not establish that members of the Trump campaign conspired or coordinated with the Russian government in its election interference activities."

Though Mueller did not give a definitive answer to whether Trump obstructed justice, Barr said he and Deputy Attorney General Rod Rosenstein concluded that the investigation lacked sufficient evidence to establish Trump committed an obstruction-of-justice offense.

"While this report does not conclude that the president committed a crime, it also does not exonerate him," Barr quoted Mueller as saying in the summary he delivered to Congress on Sunday, two days after Mueller submitted the report to the attorney general.

House Speaker Nancy Pelosi and Senate Minority Leader Chuck Schumer -- the two top Democrats in Congress -- said the full report needs to be made public, arguing the summary "raises as many questions as it answers."

"The fact that special counsel Mueller's report does not exonerate the president on a charge as serious as obstruction of justice demonstrates how urgent it is that the full report and underlying documentation be made public without any further delay," they said in a joint statement.

"Given Mr. Barr's public record of bias against the special counsel's inquiry, he is not a neutral observer and is not in a position to make objective determinations about the report."

[Getty/Kyodo]

In a letter to the leadership of the House and Senate Judiciary committees on Friday, Barr said he will determine to what extent to disclose the report's contents to Congress and the public after consulting with Mueller and Rosenstein.

"I remain committed to as much transparency as possible," the attorney general said.

Since the launch of the Mueller investigation in May 2017, Trump has called it a "witch hunt" and "hoax," and insisted there was "no collusion" with Russia.

Mueller's appointment came after a report declassified in January 2017 said three U.S. intelligence agencies concluded Russian President Vladimir Putin ordered a campaign in 2016 to influence the outcome of the U.S. presidential election in Trump's favor over Democratic candidate Hillary Clinton.