WASHINGTON, Nov 9 (Reuters) - Steve Bannon, a former senior adviser to President Donald Trump, appeared before a federal appeals court on Thursday in an attempt to overturn his conviction for failing to comply with a congressional subpoena related to the investigation of the Jan. 6, 2021, attack on the U.S. Capitol.

Bannon, who was found guilty last year of two misdemeanor counts of contempt of Congress, argued that he was denied a fair trial because the judge prevented him from presenting key defense arguments, including his claim that his lawyer advised him not to comply with the subpoena.

His attorney, David Schoen, told the three-judge panel of the U.S. Court of Appeals for the District of Columbia Circuit that Bannon had acted within the confines of the law.

Judge Cornelia Pillard raised questions about Bannon's relevancy to the riot, noting that he was not working in the White House at the time and that the committee's requests were largely unrelated to his interactions with Trump.

Prosecutors successfully argued during the trial that Bannon's claimed executive privilege defense was irrelevant as the focus was on his deliberate refusal to cooperate with the subpoena, regardless of his reasons for doing so.

Bannon, who did not attend the hearing, was sentenced to four months in prison and a $6,500 fine by U.S. District Judge Carl Nichols in October 2022. However, he was allowed to remain free while his appeal is pending.

Outside the courthouse, Schoen expressed his intention to escalate the appeal process if the panel rejects Bannon's appeal. He stated that they would request a review by the full D.C. Circuit court and, if necessary, appeal to the U.S. Supreme Court.

Once a prominent figure in right-wing media, Bannon served as Trump's chief White House strategist in 2017 before their relationship deteriorated, only to mend later. Despite their fallout, Bannon remains a popular figure among the American right.

The congressional committee sought information from Bannon regarding his alleged discussions with members of Congress about obstructing the certification of the 2020 presidential election results. Bannon had also predicted that chaos would ensue on the day of the Capitol riot.

During the attack, supporters of Trump assaulted police officers, breached barricades, and ransacked the Capitol in an unsuccessful attempt to undermine the certification of President Joe Biden's victory.

Prosecutors argued that Trump did not fully invoke executive privilege to protect Bannon's testimony, and much of the information sought from him was not shielded due to his departure from the administration before the attack occurred.

The House committee ultimately disbanded at the end of 2022 without obtaining the requested information from Bannon.