Then US president Donald Trump watched the deadly attack on the US Capitol unfold for hours, ignoring pleas from his children and other close advisers to urge his supporters to stop the violence, witnesses have told a congressional hearing.

Te US House of Representatives committee that is probing Mr Trump’s alleged involvement in the January 6, 2021, attack also revealed bombshell previously unseen footage of the then president’s response to the angry mob.

“I don’t want to say the election’s over,” he said in outtakes from video footage of his statement from the day after the riot, in which he refused to accept losing the 2020 election.

The clips were part of a production of a speech where Mr Trump refused to say results of the presidential election had not been settled and attempted to call the rioters patriots.

The committee also used its eighth hearing on Thursday (local time) to detail what members said was Mr Trump’s failure to act for the 187 minutes between the end of his inflammatory speech at a rally urging supporters to march on the Capitol, and the release of a video telling them to go home.

“President Trump sat at his dining table and watched the attack on television while his senior-most staff, closest advisers and family members begged him to do what is expected of any American president,” said Elaine Luria, a Democratic committee member, on Thursday (local time).

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Committee chairman Bennie Thompson went further.

“He lied, he bullied, he betrayed his oath. He tried to destroy our democratic institutions,” he said via video, after recently testing positive for COVID.

“And then he stopped for 187 minutes on January 6.

“He could not be moved to rise from the dining room table and walk the few steps down the White House hallway into the press briefing room, where cameras were anxiously and desperately waiting to carry his message to the armed and violent mob.”

The panel played videotaped testimony from White House aides and security staff discussing the events of the day.

Former White House counsel Pat Cipollone was asked question after question in the recorded testimony about what Mr Trump did or didn’t do: Did he call the secretary of defence? Did he call the US attorney-general? Did he call the head of Homeland Security? Mr Cipollone answered no each time.

Panel members said Mr Trump’s daughter Ivanka and son Don Jr were among those who pleaded with him to act.

The hearing, expected to be the last until September, detailed both the violence that played out as Trump supporters fought their way into the Capitol and Mr Trump’s actions in the hours after his speech in which he urged the crowd to “fight like hell” and the release of the video telling the rioters to go home.

The onslaught on the Capitol, as then vice-president Mike Pence met with lawmakers, injured more than 140 police officers and delayed certification of Democratic President Joe Biden’s victory in the November 2020 election.

“Over the last month and a half, the select committee has told a story of a president who did everything in his power to overturn an election. He lied, he bullied, he betrayed his oath,” the committee’s Democratic chairperson, Representative Bennie Thompson, said via a remote video feed after being diagnosed with COVID.

“He tried to destroy our democratic institutions. He summoned a mob to Washington.”

Adam Kinzinger, a Republican committee member, said Mr Trump had no interest in calling off the rioters.

“The mob was accomplishing President Trump’s purpose, so of course he didn’t intervene,” Mr Kinzinger said.

Mr Trump remains highly popular among Republican voters and continues to flirt with the possibility of running for president again in 2024. But a Reuters/Ipsos poll concluded on Thursday found his standing among Republicans had weakened slightly since the hearings began early last month.

Mr Trump denies wrongdoing and continues to claim falsely that he lost because of widespread fraud.

Scheduled at night to reach a broad television audience, the public hearing was the eighth in six weeks by the House of Representatives select committee.

Another round of hearings will begin in September, the panel’s Republican vice-chair, Liz Cheney, said.

The witnesses in the room were Matthew Pottinger, a deputy national security adviser under Trump, and Sarah Matthews, a deputy press secretary in his White House. Both resigned in the hours following the riot.

“If the president had wanted to make a statement and address the American people, he could have been on camera almost immediately,” Mr Matthews testified.

“If he had wanted to make an address from the Oval Office, we could have assembled the White House press corps within minutes.”

The panel of seven Democratic and two Republican House members has been investigating the attack for the past year.

It has used the hearings to build a case that Mr Trump’s efforts to overturn his defeat by Mr Biden in 2020 constitute illegal conduct, far beyond normal politics.

– with AAP