WASHINGTON -- The judge in the criminal trial of Steve Bannon, Donald Trump's prominent former presidential adviser, told defence lawyers on Wednesday not to turn the case into a "political circus" as they prepared to cross-examine a lawyer for the U.S. congressional panel whose subpoena he defied last year.

Bannon, 68, has pleaded not guilty to two misdemeanour counts of contempt of Congress. Opening statements and testimony from the prosecution's first witness in the trial came on Tuesday.

Federal prosecutors on Wednesday resumed their questioning of Kristin Amerling, chief counsel of the Democratic-led House of Representatives select committee investigating the Jan. 6, 2021, attack on the U.S. Capitol by Trump supporters.

Amerling told the jury on Tuesday that Bannon missed two key deadlines in October 2021 to provide documents and testimony sought in a subpoena issued by the committee the prior month.

Prosecutor Amanda Vaughn on Tuesday told jurors that Bannon believes he is "above the law" and that he willfully failed to comply with the committee's subpoena as it investigates the attack. Bannon's attorney Evan Corcoran told the jury in his opening statement that his client is innocent of the charges.

Before testimony resumed on Wednesday, Vaughn told U.S. District Judge Carl Nichols that she was concerned over comments that Corcoran made in his opening statement on Tuesday suggesting that the case against Bannon was motivated by political bias.

In those comments, Corcoran urged jurors to consider if statements by prosecution witnesses are "affected by politics."

Vaughn on Wednesday accused the defence of trying to circumvent the judge's pre-trial rulings aimed at keeping politics out of the case.

"It seems the defendant is trying to find ways around it," Vaughn said, saying she feared the defence is trying to turn the trial into a "political circus."

Nichols told the lawyers in the case: "I do not intend for this to become a political case, a political circus."

Amerling resumed her testimony on Wednesday, saying that the committee wanted to hear from Bannon because he was identified as one of the people who attended a planning meeting at a Washington hotel the day before the Capitol attack. Amerling also noted Bannon's comments on his "War Room" podcast in which she said he repeated false claims that the election had been "stolen."

Trump's supporters stormed the Capitol and attacked police in a failed effort to block formal congressional certification of his 2020 election loss to Democrat Joe Biden.

As a top adviser to the Republican Trump's 2016 presidential campaign who later served as White House chief strategist, Bannon helped articulate the "America First" right-wing populism and fierce opposition to immigration that helped define Trump's presidency.

The presentation of the prosecution's case is not expected to last long. After Amerling is done testifying, the prosecution is expected to call an FBI agent and may also call an additional committee staffer, according to court filings.

It is not yet clear what witnesses, if any, Bannon's defence team would call. His attorneys have pushed for permission to compel the House committee's chairman, Democratic Representative Bennie Thompson, to take the witness stand.

"I challenge Bennie Thompson today to have the courage to come to this courthouse. If he's going to charge somebody with a crime, he's got to be man enough to show up here," Bannon said after exiting the courthouse on Tuesday.

The U.S. Justice Department pursued charges against Bannon after the Democratic-led House voted to hold him in contempt for defying the subpoena.

Reporting by Sarah N. Lynch, additional reporting by Katharine Jackson; Editing by Scott Malone and Aurora Ellis