“The reason that he agreed to testify privately for the intelligence committees is, first and foremost, because he owes them,” one of the people familiar with Cohen’s plans said. “He pleaded guilty to lying to them and owes them an apology.” Cohen admitted in court late last year that he lied to Congress when he told them that negotiations to build a Trump Tower Moscow ended in January 2016, and that he hadn’t discussed it much with Trump. In fact, Cohen testified, he agreed to travel to Russia in connection with the Moscow project and took steps to prepare for Trump’s possible trip there after he clinched the Republican nomination.

Cohen is “more open to answering questions” about these and other Russia-related issues than he would have been in a public setting, according to this source, as long as he remains “secure in the knowledge that both committees will protect his testimony and prevent leaks.”

Read: Michael Cohen takes Mueller inside the Trump Organization

The Senate panel, which subpoenaed Cohen earlier this month, and its House counterpart declined to preview what questions they intend to ask. But the central purpose of the interviews is for Cohen to correct the record on his previous false statements to the committees about the timing of the Trump Tower Moscow negotiations—and, crucially, whether Trump or anyone in the White House directed him to lie in the first place. BuzzFeed News reported earlier this month that Mueller had evidence that Trump had asked Cohen to lie about the timing of the real-estate deal, prompting the special counsel’s office to release a rare statement contradicting aspects of the story. But House Democrats made it clear that, if it were confirmed that the president had tried to obstruct justice in order to hide his involvement in business negotiations with the Kremlin during the election—while Russia waged a hacking and disinformation campaign to undermine Trump’s opponent—it would be cause for impeachment.

Democratic Representative Adam Schiff, the chairman of the House Intelligence Committee, told MSNBC on Wednesday morning that the panel expects Cohen to address the Moscow real-estate deal, which was also a potential source of leverage for Russia throughout 2016 as Trump—and his family—kept the negotiations a secret from voters. Cohen admitted late last year to discussing the Moscow deal with Trump’s family members “within” the Trump Organization.

Donald Trump Jr., an executive vice president of the Trump Organization, told the Senate Judiciary Committee that he was only “peripherally aware” of the Moscow deal in 2016. It is not clear what he told the House Intelligence Committee, which has not yet released the transcripts of the closed-door interview. But Cohen’s corrected testimony could illuminate whether other witnesses have been honest during congressional testimony about their role in, or knowledge of, the Trump Tower Moscow negotiations in 2016, and Russia’s interference more broadly.