WASHINGTON — A Democratic US congressional committee chairman said on Thursday he may hold Attorney General William Barr in contempt of Congress if he does not hand over a complete version of Special Counsel Robert Mueller’s report on Russian interference in the 2016 presidential election.

Barr canceled his scheduled appearance on Thursday before the House of Representatives Judiciary Committee after clashing with Democratic Chairman Jerrold Nadler over the format of the hearing. Barr testified on Wednesday before the Republican-led Senate Judiciary Committee, stoutly defending Republican President Donald Trump in the wake of the release of the Mueller report.

“We will have no choice but to move quickly to hold the attorney general in contempt if he stalls or fails to negotiate in good faith,” Nadler said at the outset of a brief meeting held in place of Barr’s testimony.

Nadler painted the confrontation with Barr in stark terms.

“Ladies and gentleman, the challenge we face is that the president of the United States wants desperately to prevent Congress, the co-equal branch of the government, from providing any check whatsoever to even his most reckless decisions,” Nadler said.

“He is trying to render Congress inert as a separate and co-equal branch of government. The challenge we face is that if we don’t stand up to him together today we risk forever losing the power to stand up to any president in the future. The very system of government of the United States, the system of limited power, the system of not having a president as a dictator is very much at stake,” Nadler said.

Nadler’s comments indicated that Democrats are prepared to escalate a showdown with Trump’s administration, which has resisted their demands for documents and information on a wide range of topics, from Trump’s taxes to his potential financial conflicts of interest.

The Justice Department said on Wednesday it would not comply with a subpoena issued by Nadler’s committee seeking an unredacted copy of Mueller’s report and evidence gathered in the 22-month investigation. Democrats have said they may issue a subpoena to try to force Barr to testify before their committee.

Barr, whose on April 18 released a version of the report with parts blacked out to protect sensitive information, spent more than four hours at a Senate hearing on Wednesday defending his handling of the report on Russia’s interference in President Donald Trump’s favor and whether Trump subsequently tried to obstruct Mueller’s probe.

The report, almost two years in the making, detailed a series of acts by Trump to impede the probe, but did not conclude whether those actions constituted the crime of obstruction. It did find that Trump and his campaign did not engage in a criminal conspiracy with Moscow.

Barr is under fire for how he characterized the Mueller report in a summary on March 24, several weeks before the findings were released. Trump seized on Barr’s summary to declare he had been fully exonerated.

Democrats have said Barr gave misleading testimony to Congress about criticism he received from Mueller over the handling of the disclosure of the report’s conclusions.

Former US Vice President Joe Biden, among those seeking the Democratic Party’s 2020 presidential nomination, on Wednesday night called for Barr’s resignation, the Washington Post reported.

Barr’s decision to skip Wednesday’s House appearance came after the committee adopted a more aggressive format with an extra hour of questioning from committee lawyers, in addition to those from the panel’s lawmakers.

The Justice Department on Wednesday called the conditions “unnecessary” and staff questions inappropriate.

The department also refused to comply with a subpoena seeking Mueller’s full, unredacted report and underlying investigative files from the probe.

Lawmakers are also seeking testimony from Mueller as soon as this month. — Reuters