President Donald Trump shared "crazy" voter fraud conspiracy theories with his aides after losing the 2020 US election, his senior law-enforcement official said in testimony aired on Monday.
Former attorney general William Barr, appearing in a recorded deposition at a congressional hearing into the 2021 assault on the US Capitol, said Mr Trump had no interest in "actual facts".
"I was demoralised because I thought, boy ... he's become detached from reality if he really believes this stuff," said Mr Barr in evidence to the House committee investigating the January 6 insurrection by supporters of Mr Trump.
Mr Barr compared the job of addressing Mr Trump's allegations with playing the game "whack-a-mole".
"When I went into this and would tell him how crazy some of these allegations were, there was never an indication of interest in the actual facts," he said.
The panel is holding six hearings in June to outline its case that the riot at the seat of US democracy in Washington was the culmination of a seven-step conspiracy by Mr Trump and his circle to overturn his defeat by Democrat Joe Biden.
Mr Trump repeatedly ignored advice from aides against claiming the November 2020 election was stolen, according to testimony given to the panel.
"We will tell the story of how Donald Trump lost the election — and knew he lost the election — and as a result of his loss, decided to wage an attack on our democracy," the committee's Democratic chairman Bennie Thompson said in his opening remarks.
Mr Trump released his first extended reaction to the investigation on Monday evening, with a 12-page statement in which he called the panel a "mockery of justice" and a "Kangaroo Court hoping to distract the American people from the great pain they are experiencing".
The second of six hearings was shown recorded accounts from the former president's advisers, including Mr Barr and campaign manager Bill Stepien, saying they repeatedly advised him not to declare victory on election night because he had not won — but that Mr Trump did so anyway.
"He thought I was wrong, he told me so, and that they were going to go in a different direction," Mr Stepien said.
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Mr Thompson's deputy on the panel, Republican Representative Liz Cheney, said Mr Trump chose to listen to the advice of "apparently inebriated" former New York mayor Rudy Giuliani "to just claim he won, and insist that the vote counting stop — to falsely claim everything was fraudulent".
Mr Trump started pushing what came to be known as his "Big Lie" around 2.30am on November 4, 2020, declaring victory on the night of an election he lost to Mr Biden by seven million votes.
Mr Barr said in his testimony that Mr Trump claimed major fraud "right out of the box on election night ... before there was actually any potential of looking at evidence."