Donald Trump 's close ally Steve Bannon has been found guilty of contempt of Congress.
Bannon was once Trump's right-hand man, helping him to win the 2016 election and advising him after he entered the White House.
He is now facing two years in jail after refusing to assist the committee investigating last year's Capitol riots, which Trump inspired with his false electoral fraud claims.
The 68-year-old has been convicted of two misdemeanour counts of contempt of Congress after he defied a subpoena from the committee.
Each contempt of Congress count is punishable by 30 days to one year behind bars, as well as a fine of between around £83 and £83,000.
Reacting to his conviction, Bannon told reporters: "We lost a battle here today. We're at war."
He castigated the "members of that show-trial committee" who he said "didn't have the guts to come down here and testify in open court".
Bannon elected not to testify in his own defence.
After the verdict, David Schoen, one of Bannon's lawyers, promised his client will have "a bullet-proof appeal."
US District Judge Carl Nichols set a sentencing date of October 21.
Trump previously asked his allies not to cooperate with the committee, accusing it of trying to hurt him politically, and several of them rebuffed the panel.
Bannon was seen as the former President's Svengali for his first few months in office, however they fell out after he criticised Trump in Michael Wolff's book Fire and Fury.
However, the pair later rebuilt their relationship and Bannon has remained loyal to Trump.
Bannon's defence team suggested to jurors that their client was a political target and claimed the prosecution's main witness was a biased Democrat.
However, prosecutors said Bannon showed disdain for the authority of Congress and needed to be held accountable for his unlawful defiance.
Prosecutor Molly Gaston told jurors the attack represented a "dark day" for America, adding: "There is nothing political about finding out why Jan. 6 happened and making sure it never happens again."
Evan Corcoran, one of Bannon's attorneys, told jurors, "The question is, 'Why? Why was Steve Bannon singled out?"
Trump previously pardoned Bannon during his final hours in office.
His aide had been charged with swindling Trump supporters over an effort to raise private funds to build the president's wall on the US-Mexico border.
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The charges of wire fraud and money laundering related to a 'We Build The Wall' fundraising campaign which prosecutors in the US Attorney's office said defrauded hundreds of thousands of donors.
Bannon's latest conviction may strengthen the position of the committee investigating the Capitol riot as it seeks to secure testimony and documents from others in Trump's orbit.
A jury of eight men and four women found Bannon guilty after less than three hours of deliberations.
It marked the first successful prosecution for contempt of Congress since 1974, when a judge found G. Gordon Liddy, a conspirator in the Watergate scandal that prompted President Richard Nixon's resignation, guilty.
Bannon, once the editor of alt-right website Breitbart, served as White House chief strategist under Donald Trump for the first seven months of his administration.
He also ran Trump's successful presidential campaign in 2016.
