A U.S. House committee convened briefly on Thursday without Attorney General William Barr in attendance to discuss his handling of the Mueller report at a time of rising tensions between Donald Trump's administration and Congress.

A day after Barr appeared at a Senate hearing to defend his handling of the report on Russian meddling in the 2016 U.S. election, the House's judiciary committee opened a similar session expected to feature an empty chair at the witness table.

Committee chair Jerry Nadler urged Barr to comply with the panel's demands to testify before it and release special counsel Robert Mueller's full report on the Russia inquiry.

"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," said Nadler.

He 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."

Barr's decision to skip Wednesday's House appearance came after the committee opted for a 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.

Speaker of the House Nancy Pelosi talks to the media at a news conference on Capitol Hill in Washington. (J. Scott Applewhite/Associated Press)

The conflict between the sides was heightened Thursday after the abbreviated session and House Speaker Nancy Pelosi's weekly news conference.

"What is deadly serious about it is the attorney general of the United States of America was not telling the truth to the Congress of the United States, and that's a crime," said Pelosi, of California.

The blunt statement was notable coming from Pelosi, who has often tried to tamp down the aggressiveness of some of the House Democrats in her charge who would like to impeach Trump.

Justice Department spokesperson Kerri Kupec called Pelosi's allegation "reckless, irresponsible and false."

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.

When asked by Democrat Charlie Crist at an April 9 hearing in the House if he knew the source of reports that the special counsel team was frustrated with Barr's summary, the attorney general stated, "No, I don't."

At an April 20 hearing, Barr told Sen. Chris Van Hollen of Maryland that he didn't know "whether Mueller supported my conclusions."

It has been learned this week that Mueller wrote to Barr about the summary on March 27, expressing the opinion it sowed public confusion and threatened to undermine confidence in the investigation.

Republicans denounce 'stunt'

Nadler said after Thursday's short hearing that they would continue to make a "good faith" offer to the administration for their request, but it would only be a matter of days before they'd take more serious steps if they continued to be stonewalled.

The top Republican on the committee, Doug Collins of Georgia, angrily denounced Nadler's characterization. He called the demands of the Democrats regarding the questioning of Barr unreasonable and deemed Thursday's session a "circus political stunt."

"They want it to look like an impeachment hearing because they won't bring impeachment proceedings," Collins said, referring to the process laid out in the Constitution for removing a senior official from office.

"The reason Bill Barr is not here today is that the Democrats decided they didn't want him here today," Collins added.

Republican Doug Collins, left, blasted Nadler and the Democrats in his opening remarks. Collins has said allowing the Democrats to have staff lawyers gives the proceedings the appearance of an impeachment hearing. (Andrew Harnik/Associated Press)

After the hearing, House Democrats took turns denouncing Barr to reporters outside the hearing room

"As a former police chief … it was painful and disgraceful to see the nation's top cop abandon his responsibilities, to allow an empty chair to speak for him this morning," said Florida Congresswoman Val Demings.

Sheila Jackson Lee of Texas said Nadler's approach showed the Democrats were willing to work with the administration and weren't rushing toward impeachment of either Barr or Trump.

Tennessee's Steve Cohen opted for theatre, bringing a rubber chicken to emphasize Barr's reluctance to testify.

Judiciary committee chair Jerry Nadler is shown before the brief session with Democratic colleague Steve Cohen, who brought with him a bucket of chicken and a rubber chicken. (Andrew Harnik/Associated Press)

The Democrats have said there was precedent for committee staff to question cabinet-level officials and Senate-confirmed officials, citing political scandals including the Watergate break-in of the 1970s and the Iran-Contra scandal of 1987.

Senate Republicans employed an outside lawyer last year for the questioning of Christine Blasey Ford, who accused Supreme Court nominee Brett Kavanaugh of sexual assault.

At the Senate hearing, Barr defended his handling of the Mueller report on Russia's interference in President Donald Trump's favour and whether Trump subsequently tried to obstruct Mueller's probe.

On April 20th, I asked Barr, “Did Bob Mueller support your conclusion?” His answer was, “I don’t know whether Mueller supported my conclusion.”<br> <br>We now know Mueller stated his concerns on March 27th, and that Barr totally misled me, the Congress, and the public. He must resign. <a href="https://t.co/rod404BbYo">pic.twitter.com/rod404BbYo</a> —@ChrisVanHollen

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.

Former U.S. 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.

Senators Elizabeth Warren and Kamala Harris, also running for the nomination, also called for him to step down.

The House judiciary committee is also seeking testimony from Mueller as soon as this month.