WASHINGTON — Donald Trump intends to assert executive privilege in a congressional investigation into the Jan. 6 insurrection at the Capitol, a move that could prevent the testimony of onetime aides, according to a letter sent by lawyers for the former president.

The letter went to at least some witnesses who were subpoenaed by the House committee, and it makes clear that Trump plans to invoke privileges meant to protect presidential communications from being shared with Congress. The substance of the letter was described Thursday by a person who has seen it and who spoke on condition of anonymity to The Associated Press because the letter was not yet public.

Spokespeople for Trump did not immediately return messages seeking comment.

The move sets the stage for a likely clash with House Democrats who are investigating the roles of Trump and his allies in the run-up to the riot, when thousands of Trump supporters broke into the Capitol as Congress was certifying the results of the presidential election won by Democrat Joe Biden.

The committee, which was formed over the summer, issued subpoenas last month to Mark Meadows, Trump's former chief of staff; Dan Scavino, the former deputy chief of staff for communications; Kashyap Patel, a former Defense Department official; and Steve Bannon, a former Trump adviser.

Politico reported the existence of the letter earlier Thursday, the deadline the committee set for compliance.

It was not immediately clear how witnesses would respond to Trump's decision to invoke executive privilege or what consequences that would face if they refuse to cooperate. Because Trump no longer is in office, he cannot directly assert privilege to keep witnesses quiet or documents out of the hands of Congress.

As the current president, Biden will have some say in the matter.

The committee has issued more than a dozen subpoenas to people linked to plans for the Jan. 6 protests, including three additional witnesses announced Thursday. Those individuals would be less likely to get help from Trump’s executive privilege claims, which would be limited to people who worked in the White House.

The committee chairman, Rep. Bennie Thompson, D-Miss., said subpoenas had gone to Ali Abdul Akbar, also known as Ali Alexander, and Nathan Martin, as well the organization “Stop the Steal,” to learn more about a rally that was planned on the Capitol grounds at the same time as the larger gathering on the National Mall. The committee has subpoenaed 11 other individuals connected to the planning of that larger rally.

According to the committee, Alexander released a statement after the riot linking “Stop the Steal” to the Capitol rally permit and explaining that the intention was to direct attendees of the larger rally to march to the Capitol.

Alexander has claimed lawmakers helped him plan the rally that led to the siege on the Capitol. He has been in Trump’s orbit for a few years, even being among the participants of Trump’s “Presidential Social Media Summit” in July 2019 that included dozens of other conservative voices and far-right provocateurs.

Meanwhile, CNN reported, citing three sources with knowledge, that Facebook whistleblower Frances Haugen will meet with the select committee. It wasn’t clear when the interview would happen, but the cable news network said it could take place as early as Thursday.

A former product manager at Facebook, Haugen leaked internal research to The Wall Street Journal and federal regulators showing the company was aware of the harm its platforms can cause while it publicly downplayed its negative impact. She did an interview with CBS’ “60 Minutes” that aired Sunday and testified before Senate Subcommittee on Consumer Protection, Product Safety and Data Security, accusing her former employer of putting profits above people’s safety and well-being.

While much of her testimony Tuesday focused on the effects of Facebook and Instagram on children and teenagers, she also has criticized the company’s decision to remove safeguards after the presidential election that aimed to prevent misinformation, foreign interference and violence, as well as its decision to disband the civic integrity unit she worked for.

Facebook says Haugen is mischaracterizing the research findings.

Asked about the meeting with Haugen, Rep. Stephanie Murphy, D-Fla., who sits on the committee, told Spectrum News the panel is trying gain a thorough of understanding of what happened on Jan. 6. 

“How did we find ourselves in the place that we did on Jan. 6?” she said. “Then, what’s the way forward to ensure that we don’t have another Jan. 6, where our democracy is on the precipice? So the Facebook interviews, just like all the other interviews, are an effort to collect data, to understand the roles of the various entities and in this case, a social media entity.”