During Thursday's hearing, the House select committee is expected to show outtakes from former President Donald Trump's recorded message delivered on Jan. 7, in which he condemned the attack on the Capitol and pledged a "seamless transition of power."

But sources familiar with their contents tell ABC News that Trump had to be pressured to condemn the attack, taking about an hour to record this message: "The demonstrators who infiltrated the Capitol have defiled the seat of American democracy. To those who engaged in the acts of violence and destruction, you do not represent our country."

Sources say Trump argued with aides as the statement was being written and wanted to call the attackers patriots. -- ABC News Chief Washington Correspondent Jonathan Karl

Just ahead of Thursday's hearing, committee member Rep. Pete Aguilar, D-Calif., said Americans can expect to learn "exactly what was happening" on Jan. 6 from when former President Donald Trump left his rally to his address in the Rose Garden three hours later.

"Where was the president at? Who was talking to him? What was he saying?" Aguilar told anchor Linsey Davis on ABC News Live Prime. "Those are the types of details that we want to get to, because while the Capitol was being overrun and law enforcement officers were providing the last line of defense to save democracy, I think it's important that the American public knows what was going on at the White House."

Aguilar said the hearing will also address Trump's statements on social media the day after the attack.

"The statements and addresses that he made on Jan. 6 and Jan. 7 are both important to his state of mind at the time and what he was willing to say and more importantly, what he wasn't willing to say," he said.

Aguilar said the committee continues to receive investigative material that may come out.

"To the extent that we need to share that with the American public, we plan to do that," he said. "Our responsibility is to find the truth here. And that's what we plan to do."

As the House select committee's last scheduled session gets underway, Steve Bannon, a former top political adviser in Donald Trump's White House, is currently on trial for defying a subpoena in connection with its investigation.

Bannon was subpoenaed by the Jan. 6 panel for records and testimony and ultimately charged with two counts of criminal contempt of Congress.

His defense attorney, David Schoen, said in court Thursday that Bannon wanted to testify but decided not to based on the advice of his attorney at the time, who reportedly told Bannon that "executive privilege had been invoked and he was not permitted by law to comply with the subpoena."

The House committee and federal prosecutors have said the executive privilege claims never covered Bannon, since the insurrection occurred long after he left his post as chief White House strategist in 2017.

Ahead of the contempt trial, Bannon had said he would be willing to testify in a live, public hearing.

Closing arguments and jury instructions in the trial are planned for Friday morning.

A revelation about deleted text messages by the Secret Service is looming large over Thursday’s hearing.

The House committee subpoenaed the agency earlier this month for text messages sent on Jan. 5 and Jan. 6, 2021. But the agency said most of those records were lost in a planned data migration.

So far, the Secret Service has provided a single text exchange to the Department of Homeland Security inspector general investigating the agency's record-keeping, according to an agency letter to the House Jan. 6 committee obtained by ABC News on Wednesday.

The committee is suggesting the Secret Service broke federal records keeping laws. Hours before the hearing, news broke that the Department of Homeland Security's inspector general has turned the inquiry into a criminal investigation.