Former White House chief strategist Stephen Bannon on Tuesday morning went behind closed doors with the House Intelligence Committee to testify in the panel’s ongoing investigation into Russian interference in the presidential election.

Bannon, who joined the Trump campaign in August of 2016, is expected to face a grilling on comments he made to Michael Wolff, the author of a controversial new book about the Trump White House.

Bannon told Wolff that a June 2016 meeting at Trump Tower between campaign officials and a Russian lawyer believed to have political dirt on Hillary Clinton Hillary Diane Rodham ClintonWhat Senate Republicans have said about election-year Supreme Court vacancies Bipartisan praise pours in after Ginsburg's death Trump carries on with rally, unaware of Ginsburg's death MORE was “treasonous.”

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"The three senior guys in the campaign thought it was a good idea to meet with a foreign government inside Trump Tower in the conference room on the 25th floor—with no lawyers," Bannon said, according to Wolff’s account. “Even if you thought that this was not treasonous, or unpatriotic ... you should have called the FBI immediately.”

Further, Bannon added, “the chance that [Donald Trump Jr. Don John Trump'Tiger King' star Joe Exotic requests pardon from Trump: 'Be my hero please' Zaid Jilani discusses Trump's move to cancel racial sensitivity training at federal agencies Trump International Hotel in Vancouver closes permanently MORE] did not walk these jumos up to his father's office on the twenty-sixth floor is zero.”

Lawmakers will press Bannon on what the president knew about that meeting, long a flashpoint in the controversy surrounding the Trump campaign’s ties to Russia, as well as any financial crimes that may have been committed.

“Specifically what's the basis for his assertion that the president met with the participants in the Trump Tower meeting,” the committee’s top Democrat, Adam Schiff Adam Bennett SchiffTop Democrats call for DOJ watchdog to probe Barr over possible 2020 election influence Overnight Defense: Top admiral says 'no condition' where US should conduct nuclear test 'at this time' | Intelligence chief says Congress will get some in-person election security briefings Overnight Defense: House to vote on military justice bill spurred by Vanessa Guillén death | Biden courts veterans after Trump's military controversies MORE (Calif.), told ABC News's Pierre Thomas. “What [Bannon] knows about the president’s knowledge of that meeting, as well as his concerns over money laundering which has been a persistent concern of ours as well.”

Former Trump campaign chairman Paul Manafort Paul John ManafortOur Constitution is under attack by Attorney General William Barr Bannon trial date set in alleged border wall scam Conspicuous by their absence from the Republican Convention MORE and his deputy, Richard Gates, have both been charged with money laundering as part of special counsel Robert Mueller Robert (Bob) MuellerCNN's Toobin warns McCabe is in 'perilous condition' with emboldened Trump CNN anchor rips Trump over Stone while evoking Clinton-Lynch tarmac meeting The Hill's 12:30 Report: New Hampshire fallout MORE’s federal investigation into potential campaign collusion with Russia.

There is no public indication that Bannon is under investigation by Mueller.

The committee’s interest in Bannon predates the release of Wolff’s book. He will also likely face questions about his knowledge of any contacts that Trump transition team members may have had with Russian officials, according to Schiff.

Blackwater founder Erik Prince in December detailed to investigators a January meeting he held with a Russian banker in the Seychelles, brokered by the UAE.

Prince, who described his relationship to the Trump campaign as minimal and unofficial, acknowledged that Bannon had told him about a separate December 2016 meeting between the Trump transition team and UAE officials.

But Prince, whose sister is Education Secretary Betsy DeVos Elizabeth (Betsy) Dee DeVosNEA president says Azar and DeVos should resign over school reopening guidance The Hill's 12:30 Report - Presented by Facebook - You might want to download TikTok now Former DeVos chief of staff joins anti-Trump group MORE, said he could not remember whether the conversation with Bannon took place before or after his trip to the Seychelles — an answer that left committee Democrats dissatisfied.

“We know from the Erik Prince testimony … that [Prince] had a meeting with Steve Bannon Stephen (Steve) Kevin BannonJuan Williams: Swamp creature at the White House Engineers say privately funded border wall is poorly constructed and set to fail: report Bannon and Maxwell cases display DOJ press strategy chutzpah MORE before he made that trip to the Seychelles traveling halfway around the world to have what he described essentially as a coincidental meeting with a Russian in a bar,” Schiff told ABC News.

“Which just happened to be a head of one of the Russian Investment Banks, so we'd like to know whether Steve Bannon was involved in establishing any kind of a back channel of with the Russians.”

Prince described the arrangement of his meeting with Kirill Dmitriev as informal, telling investigators that the real purpose of his trip was to meet with Emirati officials to discuss terrorism in the area and “conceptual-only stuff” on mineral-related business.

“It was a matter of, ‘Hey, while you’re here, there’s a Russian guy that we’ve done some business with in the past, and it’d be interesting for you to meet him,’” Prince told investigators.

Bannon is not the only Trump campaign associate expected to interview before the committee this week. Former campaign manager Corey Lewandowski Corey R. LewandowskiHow Trump can win reelection: Focus on Democrats, not himself Trump Jr. distances from Bannon group, says he attended 'single' event Bannon, three others charged with defrauding donors of 'We Build The Wall' campaign MORE is also expected to appear.

The Bannon interview was scheduled to begin at 9:30 on Tuesday morning.