WASHINGTON (Reuters) - Attorney General William Barr on Wednesday canceled plans to testify before the House of Representatives about his handling of Special Counsel Robert Mueller’s Russia investigation, further inflaming tensions between U.S. President Donald Trump and Democrats in Congress.

Barr was due to face the Democratic-controlled House Judiciary Committee on Thursday, but pulled out after the two sides were unable to agree on the format for the hearing.

“It’s simply part of the administration’s complete stonewalling of Congress,” Judiciary Committee Chairman Jerrold Nadler told reporters.

Justice Department spokeswoman Kerri Kupec said Nadler’s proposal to have committee lawyers question Barr was “unprecedented and unnecessary,” saying questions should come from lawmakers.

The Justice Department also said on Wednesday it would not comply with a Nadler-issued subpoena seeking an unredacted version of Mueller’s report and underlying investigative files from the probe.

Earlier on Wednesday, Barr spent more than four hours before the Republican-controlled Senate Judiciary Committee where he fended off Democratic criticism of his decision to clear Trump of criminal obstruction of justice and faulted Special Counsel Robert Mueller for not reaching a conclusion of his own on the issue.

In his first congressional testimony since releasing a redacted version of Mueller’s report on April 18, Barr also dismissed Mueller’s complaints that he initially disclosed the special counsel’s conclusions on March 24 in an incomplete way that caused public confusion.

Illustrating tensions between the two men, Barr described as “a bit snitty” a March 27 letter from Mueller in which the special counsel urged him to release broader summaries of his findings - a step Barr rejected. Trump seized on Barr’s March 24 letter to declare that he had been fully exonerated.

Several Democrats on the Senate committee called for Barr’s resignation.

Democrats have accused Barr of trying to protect the Republican president, who is seeking re-election next year. They pressed Barr on why he decided two days after receiving the 448-page document from Mueller in March to conclude that Trump had not unlawfully sought to obstruct the 22-month investigation.

“I don’t think the government had a prosecutable case,” Barr said.

‘ALLEGATIONS NOW PROVEN FALSE’

The report detailed extensive contacts between Trump’s 2016 presidential campaign and Moscow and the campaign’s expectation that it would benefit from Russia’s actions, which included hacking and propaganda to boost Trump and harm Democratic candidate Hillary Clinton. The report also detailed a series of actions Trump took to try to impede the investigation.

Mueller, a former FBI director, concluded there was insufficient evidence to show a criminal conspiracy and opted not to make a conclusion on whether Trump committed obstruction of justice, but pointedly did not exonerate him. Barr has said he and Rod Rosenstein, the Justice Department’s No. 2 official, then determined there was not enough evidence to charge Trump with obstruction.

Barr often appeared to excuse or rationalize Trump’s conduct, asserting that the president may not necessarily have been trying to derail Mueller’s investigation.

Democratic Senator Mazie Hirono told Barr that he had sacrificed a “once-decent reputation for the grifter and liar that sits in the Oval Office.”

Senator Lindsey Graham, the committee’s Republican chairman, rushed to Barr’s defense, telling Hirono: “You’ve slandered this man.”

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Trump had been unfairly smeared, Barr said, by suspicions he had collaborated with Russia in the election. “Two years of his administration have been dominated by the allegations that have now been proven false. To listen to some of the rhetoric, you would think that the Mueller report had found the opposite,” Barr said.

Barr was critical of Mueller for not reaching a conclusion himself on whether Trump obstructed the probe.

“I think that if he felt that he shouldn’t go down the path of making a traditional prosecutorial decision, then he shouldn’t have investigated,” Barr said.

Barr was asked about the report’s finding that Trump directed then-White House counsel Don McGahn in June 2017 to tell Rosenstein that Mueller had conflicts of interest and must be removed. McGahn did not carry out the order. Rosenstein had appointed Mueller the prior month.

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Barr, appointed by Trump after the president fired his predecessor, Jeff Sessions, seemed to minimize the incident and said Trump believed “he never outright directed the firing of Mueller.” Trump could have presumably appointed someone else to do the job after Mueller was fired, he said.

“We did not think in this case that the government could show corrupt intent,” Barr said.

‘INTENTION WAS VERY CLEAR’

Democrats on the panel were unconvinced.

“I think the president’s intention was very clear. He wanted this to end,” Senator Dick Durbin said.

Under questioning by Democratic Senator Kamala Harris, a 2020 presidential candidate, Barr acknowledged he did not review the investigation’s underlying evidence before deciding to clear Trump of obstruction.

Barr disputed the view that Mueller was handing the baton to Congress for possible impeachment proceedings. “That would be very inappropriate,” Barr said. “That’s not what the Justice Department does.”

The Democratic-controlled House would start any such impeachment effort, but Trump could not be removed from office without approval by a two-thirds majority in the Republican-controlled Senate.

Democrats also accused Barr of misleading Congress, by saying in April that he did not know whether Mueller agreed with his characterization of the report - failing to mention Mueller’s March 27 letter that Barr’s initial summary did not “fully capture the context, nature and substance of this Office’s work.”

Barr testified that Mueller was unhappy with the way the conclusions were being characterized in the media, not his account of the conclusions, although Mueller’s letter did not mention media coverage.

“The letter is a bit snitty,” Barr said, using a word meaning disagreeably ill-tempered, “and I think it was probably written by a member of his staff.”

Several Democrats demanded that Mueller testify before the committee, but Graham ruled that out.

Committee Republicans did not focus on Trump’s conduct but rather on what they saw as the FBI’s improper surveillance during the 2016 race of Trump aides they suspected of being Russian agents, as well as on the Kremlin’s election meddling.

Barr indicated that to him, the matter was closed.

“The report is now in the hands of the American people,” he said. “We’re out of it. We have to stop using the criminal justice system as a political weapon.”