The US congressional committee investigating the 2021 Capitol riot is preparing to highlight the way violent far-right extremists answered Donald Trump’s “siren call” to come to Washington for a big rally aimed at overturning the presidential election.

The panel will convene on Tuesday (US time) for a public hearing probing what it calls the final phase of Mr Trump’s multipronged effort to halt Joe Biden’s victory.

As dozens of lawsuits and false claims of voter fraud fizzled, Mr Trump tweeted the rally invitation, a pivotal moment, the committee said.

The far-right Proud Boys, Oath Keepers and others now facing criminal charges readily answered his call.

“We will lay out the body of evidence that we have that talks about how the president’s tweet on the wee hours of December 19 of ‘Be there, be wild’, was a siren call to these folks,” one panel member, Stephanie Murphy, said.

In fact, Trump tweeted, “Be there, will be wild!”.

This is the seventh hearing in a series that has presented numerous blockbuster revelations from the January 6 committee.

Over the past month, the panel has created a stark narrative of a defeated Mr Trump “detached from reality”, clinging to his false claims of voter fraud and working feverishly to reverse his election defeat.

It all culminated with the deadly attack on the Capitol, the committee says.

What the committee intends to probe on Tuesday is whether the extremist groups, including the Proud Boys, Oath Keepers and QAnon adherents who had rallied for Mr Trump before, co-ordinated with White House allies for January 6.

The Oath Keepers have denied there was any plan to storm the Capitol.

The panel is also expected to highlight new testimony from Pat Cipollone, the former White House counsel, who “was aware of every major move” Mr Trump was making, said Democrat Jamie Raskin, who will lead the session.

It is the only hearing set for this week, as new details emerge. An expected prime-time hearing for Thursday has been postponed.

This week’s session comes after former White House aide Cassidy Hutchinson provided stunning accounts under oath of an angry Mr Trump who knowingly sent armed supporters to the Capitol on January 6 and then refused to quickly call them off as violence erupted, siding with the rioters as they searched for then vice-president Mike Pence.

Mr Trump has said Ms Hutchinson’s account is not true.

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But Mr Cipollone at Friday’s private session did not contradict earlier testimony.

Mr Raskin said the panel planned to use “a lot” of Mr Cipollone’s testimony.

The panel is expected to highlight a meeting on December 18, 2020, at the White House in which former Trump lawyers Rudy Giuliani and Sidney Powell, one-time Trump national security adviser Michael Flynn and others floated ideas for overturning the election results, Mr Raskin told CBS at the weekend.

On December 19, Mr Trump would send the tweet beckoning supporters to Washington for the January 6 rally, the day Congress was set to certify the Electoral College count.

The Proud Boys and the Oath Keepers, extremist far-right groups whose leaders and others are now facing rare sedition charges for their roles in the attack, prepared to come to Washington, according to court filings.

The night before January 6, Proud Boys leader Enrique Tarrio met with Oath Keepers head Stewart Rhodes at an underground car park, according to court filings along with images a documentary filmmaker trailing the group provided to the panel.

The Oath Keepers had also been organising for January 6 and established a “quick response force” at a nearby hotel in Virginia, according to court filings.

After the Capitol siege, Mr Rhodes called someone with an urgent message for Mr Trump, another group member has said.

Mr Rhodes was denied a chance to speak to Mr Trump, but urged the person on the phone to tell the Republican president to call upon militia groups to fight to keep the president in power.

The panel has shown, over the course of fast-paced hearings and with eyewitness accounts from the former president’s inner circle, how Mr Trump was told “over and over” again, as vice-chairwoman Liz Cheney said, he had lost the election and his false claims of voter fraud were just not true.

-AAP