WASHINGTON -- The House Jan. 6 committee aims to show in its final hearing Thursday that Donald Trump's lies about a stolen election fuelled the grisly U.S. Capitol attack, which he did nothing to stop but instead "gleefully" watched on television at the White House.

The prime-time hearing will dive into the 187 minutes that Trump failed to act on Jan. 6, 2021, despite pleas for help from aides, allies and even his family. The panel intends to show how the defeated president's attempt to overturn Joe Biden's election victory has left the United States facing enduring questions about the resiliency of its democracy.

"A profound moment of reckoning for America," said Rep. Jamie Raskin, D-Md., a member of the committee.

With live testimony from two former White House aides, and excerpts from its trove of more than 1,000 interviews, the nearly two-hour session will add a closing chapter to the past six weeks of hearings that at times have captivated the nation.

Returning to prime time for the first time since the series of hearings began, the panel aims to show just how close the United States came to what one retired federal judge testifying this summer called a constitutional crisis.

The events of Jan. 6 will be outlined "minute by minute," said the panel's vice chair, Rep. Liz Cheney, R-Wyo.

"You will hear that Donald Trump never picked up the phone that day to order his administration to help," Cheney said.

"He did not call the military. His Secretary of Defence received no order. He did not call his Attorney General. He did not talk to the Department of Homeland Security," Cheney said. "Mike Pence did all of those things; Donald Trump did not."

The hearing will also show never-before-seen outtakes of a Jan. 7 video that White House aides pleaded for Trump to make as a message of national healing for the country. The footage will show how Trump struggled to condemn the mob of his supporters, who violently breached the Capitol, according to a person familiar with the matter and granted anonymity to discuss it ahead of its public release. Trump reluctantly condemned the riot in a three-minute speech that night.

Testifying Thursday will be former White House aides who had close proximity to power.

Matt Pottinger, who was deputy national security adviser, and Sarah Matthews, then press aide, both submitted their resignations on Jan. 6, 2021, after what they saw that day. Trump has dismissed the hearings on social media and regarded much of the testimony as fake.

Rep. Bennie Thompson, D-Miss., the chairman of the committee, is isolating after testing positive for COVID-19 and will attend by video. Rep. Elaine Luria, D-Va., a former Naval officer who will lead the session with Rep. Adam Kinzinger, R-Ill., who flew combat missions in Iraq and Afghanistan, said she expects the testimony from the White House aides will "just be really compelling."

"These are people who believed in the work they were doing, but didn't believe in the stolen election," Luria said.

The White House aides were not alone in calling it quits that day. The panel is expected to provide a tally of the Trump administration aides and even Cabinet members who resigned after Trump failed to call off the attack. Some Cabinet members were so alarmed they discussed invoking the 25th Amendment to remove Trump from office.

As the panel continues to collect evidence and prepares to issue a preliminary report of findings, it has amassed the most substantial public record to date of what led up to Americans attacking the seat of democracy.

While the committee cannot make criminal charges, the Justice Department is monitoring its work.

So far, more than 840 people have been charged with federal crimes related to the Capitol riot. Over 330 of them have pleaded guilty, mostly to misdemeanors. Of the more than 200 defendants to be sentenced, approximately 100 received terms of imprisonment.

What remains uncertain is whether Trump or the former president's top allies will face serious charges. No former president has ever been federally prosecuted by the Justice Department.

Attorney General Merrick Garland said Wednesday that Jan. 6 is "the most wide-ranging investigation and the most important investigation that the Justice Department has ever entered into."

"We have to get this right," Garland said. "For people who are concerned, as I think every American should be, we have to do two things: We have to hold accountable every person who is criminally responsible for trying to overturn a legitimate election, and we must do it in a way filled with integrity and professionalism."

In delving into the timeline, the panel aims to show what happened between the time Trump left the stage at his "Stop the Steal" rally shortly after 1:10 p.m., after telling supporters to march to the Capitol, and some three hours later, when he issued a video address from the Rose Garden in which he told the rioters to "go home" but also praised them as "very special."

It also expects to produce additional evidence about Trump's confrontation with Secret Service agents who refused to drive him to the Capitol -- a witness account that the security detail has disputed.

Five people died that day as Trump supporters battled the police in gory hand-to-hand combat to storm the Capitol. One officer has testified about how she was "slipping in other people's blood" as they tried to hold back the mob. One Trump supporter was shot and killed by police.

"The president didn't do very much but gleefully watch television during this time frame," Kinzinger said.

Not only did Trump refuse to tell the mob to leave the Capitol, he did not call other parts of the government for backup and gave no order to deploy the National Guard, Cheney said.

This despite countless pleas from Trump's aides and allies, including his daughter Ivanka Trump and Fox News host Sean Hannity, according to previous testimony and text messages the committee has obtained.

"You will hear that leaders on Capitol Hill begged the president for help," Cheney has said, including House Republican leader Kevin McCarthy, who she said indicated he was "'scared' and called multiple members of President Trump's family after he could not persuade the President himself."

The panel has said its investigation is ongoing and other hearings are possible. It expects to compile a preliminary report this fall, and a final report by the end of this session of Congress.