WASHINGTON (Reuters) - Congressional Democrats on Monday struck a rare deal in their wide-ranging probes of President Donald Trump, with the U.S. Justice Department agreeing to hand over more evidence from Special Counsel Robert Mueller’s Russia inquiry.

The compromise, an unusual retreat by Trump in his months-long stonewalling campaign against House Democrats, came just before a House panel heard testimony for more than four hours from John Dean, a historic figure from the Watergate era.

Before Dean spoke to the House Judiciary Committee, Trump took the opportunity on Twitter to slam the former White House counsel under President Richard Nixon as a “sleazebag attorney.” Nixon resigned the presidency in disgrace in 1974.

Dean told the panel there were parallels between Mueller’s investigative report, released in redacted form in mid-April, and a 1974 document, known as the Watergate Road Map, in which a special prosecutor laid out the case against Nixon.

“Mueller has provided this committee with a road map,” said Dean, who was part of a panel of witnesses.

Mueller’s report found Russia meddled in the 2016 U.S. presidential election and that Trump’s election campaign had multiple contacts with Russian officials. But the report found insufficient evidence to establish a criminal conspiracy between the campaign and Moscow.

The report also outlined 10 instances in which Trump tried to interfere with Mueller’s investigation but declined to make a judgment on whether that amounted to obstruction of justice.

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As part of his effort to uncover more of Mueller’s findings, Judiciary Committee Chairman Jerrold Nadler announced that his panel will get some of the evidence related to Trump’s attempts to interfere with Mueller’s probe from the Justice Department.

The committee will not see a full, unredacted copy of Mueller’s report under the agreement, said Nadler, a Democrat. But lawmakers will get access to interview notes and other evidence, including “first-hand accounts of misconduct,” Nadler said at the outset of the hearing.

The hearing, one in a series still to come on the Mueller report, occurred amid continuing discussion among House of Representatives Democrats about whether to begin impeachment proceedings against Trump.

Nadler said that under the deal with Justice he will hold off on a threat to bring criminal contempt charges against U.S. Attorney General William Barr. For weeks Barr has resisted a subpoena from Nadler’s committee for a full, unredacted version of Mueller’s 448-page final report and underlying evidence.

The Justice Department will continue to cooperate with the committee, under their agreement, as long as Democrats hold off on the contempt vote, Justice spokeswoman Kerri Kupec said.

The Democratic-controlled House will vote as previously planned on Tuesday on a measure that would increase pressure on Trump by authorizing the committee to sue the administration in federal court if needed over access to the report.

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Nadler said a lawsuit may yet be necessary and added that Tuesday’s vote may force former White House counsel Don McGahn, a central figure in Mueller’s report, to testify. McGahn resigned his White House post in August 2018.

Mueller’s investigation is part of a broad fight between Trump and congressional Democrats, who are investigating his policies, conduct in office and private businesses. Trump has vowed to fight congressional subpoenas.

Barr has said he is required by law not to release evidence obtained from grand jury proceedings, and grand jury materials were redacted from the section of the report dealing with Russian interference in the election. But this was less of a concern for the section of Mueller’s report dealing with obstruction, which was based on testimony from voluntary interviews Trump advisers and other witnesses gave to Mueller, rather than grand jury testimony.

Representative Doug Collins, the top Republican on the House Judiciary Committee, said the agreement indicated the Trump administration was not stonewalling Congress, adding that Democrats should focus on the threat from Russia.

“Democrats are abandoning their duty to confront foreign interference in our elections in favor of drawing out their slanderous campaign against the president,” he said.

In related news, the House Oversight Committee said on Monday it plans to vote on Wednesday on whether to hold Barr and Commerce Secretary Wilbur Ross in contempt of Congress for stonewalling a probe into an alleged scheme to politicize the 2020 U.S. Census.