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House Speaker Nancy Pelosi announced Thursday she will create a select committee to investigate the January 6 attack on the Capitol after Republicans blocked the formation of an independent commission.

The select committee will corral the various House Democratic investigations into the events surrounding the deadly insurrection into a single effort to examine what led to pro-Donald Trump supporters breaching the Capitol and disrupting the certification of President Joe Biden’s November 2020 election win.

Pelosi said that it had been four weeks since Senate Republicans blocked the commission, and it did not appear they would change their minds, so she was now moving forward with a select committee.

“This morning, with great solemnity and sadness, I’m announcing that the House will be establishing a select committee on the January 6 insurrection,” Pelosi said. “The select committee will investigate and report on the facts and the causes of the attack and it will report recommendations for the prevention of any future attack.”

CNN reported on Tuesday that Pelosi was moving forward with the select committee, though she denied at the time that she had made a decision yet. But two days later, Pelosi announced the committee would be formed.

The select committee is sure to set off a political battle over the investigation into the January 6 insurrection with Republicans, who have accused Democrats of continuing to investigate the events for political reasons.

“I’m sure it will be political because that’s the whole way that she’s handled it,” House Minority Leader Kevin McCarthy said Wednesday following reports Pelosi would move forward with the select committee.

But Democrats have insisted that a definitive investigation needs to be undertaken, particularly as some Republicans have tried to downplay the violence that occurred or spread conspiracy theories about who carried out the attack.

Pelosi’s decision to move forward with a select committee led by House Democrats comes after her initial effort to create an independent panel modeled after the 9/11 Commission was blocked by Senate Republicans.

In the House, 35 Republicans voted to create the independent commission after a bipartisan deal had been struck for a panel with equal representation and subpoena power. But McCarthy and Senate Minority Leader Mitch McConnell opposed the commission, and Senate Republicans filibustered the measure in a 54-35 vote, short of the 60 needed.

Pelosi said it would have been “preferable” to have an outside commission investigate the January 6 attack but that she was not worried that the select committee would dismissed as a political effort.

“I don’t worry about that at all,” Pelosi said. “I have no intention of walking away from our responsibility.”

McConnell argued on Thursday that the House’s select committee is unnecessary, telling Fox News that the move by Pelosi “is about the Democrats trying to convince the American people that we’re not going to find out what happened on January 6.”

“We were all witnesses, we know. People are being arrested, indicted, one has already pled guilty. Nobody will fail to be punished,” the Kentucky Republican said.

With a select committee, Democrats are likely to have unilateral subpoena power, just as Republicans did when they created a select committee to investigate the deadly 2012 terrorist attack on the US compound in Benghazi, Libya.

The select committee is likely to closely examine the role Trump played in the lead up to the attack, in which the former President spread lies about the 2020 election being stolen from him. But the panel could also look at the role that some House members played, including McCarthy’s conversations with Trump as the riot was unfolding.

Pelosi declined to say whether she thought the committee should call on McCarthy to testify, saying she wouldn’t get into details about what the committee would do.

Pelosi also did not name a chairman of the committee, saying that would come later. House Homeland Security Chairman Bennie Thompson, a Mississippi Democrat whose committee has been examining the attack, is seen as a potential candidate to chair the new panel.

On the Republican side, McCarthy could tap a staunch Trump ally like Rep. Jim Jordan of Ohio to be the top Republican on the select committee, rather than the Homeland Security ranking member, Rep. John Katko of New York, who negotiated the deal to create a commission.

Pelosi said that the select committee was likely to take up two investigative threads: into how White supremacy and anti-Semitism fueled the rioters, and into the security at the Capitol that day.

The commission legislation would have set an end date for the panel’s investigation of December 31, which Republicans had pushed for in an effort to wrap up the commission ahead of the 2022 midterm campaign. But Pelosi said Thursday that the select committee’s timetable would be “as long as it takes” to complete the investigation.

“We were doing it in a time frame that Republicans were comfortable with, but now another month has gone by, so we’ll just have to make the plan and see how long that takes,” she said.

This story has been updated with additional developments Thursday.

CNN’s Manu Raju and Devan Cole contributed to this report.