The agreement was a major breakthrough for the commission, which for weeks had pressed Mr. Cipollone to cooperate – and subpoenaed him last week – believing he could provide crucial testimony. Mr. Cipollone witnessed key moments in Mr. Trump’s effort to overturn the election results, including discussions of seizing voting machines and sending false letters to state officials about voter fraud. He was also in the West Wing on Jan. 6, 2021, as Mr. Trump responded to violence at the Capitol when his supporters attacked the building in his name. People close to Mr. Cipollone have repeatedly warned that concerns about executive privilege and attorney-client privilege could limit his cooperation. But committee negotiators pressed to hear from Mr. Cipollone and Patrick F. Philbin, who was his White House deputy. Mr. Cipollone will participate in a videotaped, transcribed interview, according to a person familiar with the discussions. He is not expected to testify publicly. A spokesman for the commission declined to comment. The committee’s push to hear Mr. Cipollone intensified after the testimony last week of Cassidy Hutchinson, a former aide to White House chief of staff Mark Meadows. Ms Hutchinson described detailed conversations with Mr Cipollone in which she said the adviser had expressed deep concerns about the actions of Mr Trump and Mr Meadows. Some of Mr. Trump’s allies have sought privately to challenge parts of Ms. Hutchinson’s testimony, which was the panel’s most explosive to date and was issued under oath. Mr Trump tried to invoke executive privilege – a president’s power to block the release of certain confidential communications with his advisers – to prevent his former aides from cooperating with the investigation. In April, Mr. Cipollone and Mr. Philbin both appeared for informal interviews with the committee on a limited set of topics, under an agreement reached by representatives and their representatives for Mr. Trump. The deal, according to an email reviewed by The New York Times, allowed for talks of a meeting with Jeffrey Clark, a Justice Department official who has sought to help Mr. Trump cling to office. Mr. Trump’s interactions with John Eastman, the conservative lawyer who drafted a legal strategy to overturn the election. any interactions with members of Congress; and Mr. Cipollone’s recollections of the events of January 6th. The agreement said the two men could not discuss conversations they or others had with Mr. Trump, except for an Oval Office discussion with Mr. Clark in a key meeting on Jan. 3, 2021. However, both were allowed to discuss the timeline of where they were, who they met with and the conversations they had on January 6. Assuming these conditions apply to Mr. Cipollone’s upcoming deposition, they would likely cover conversations such as those he may have had with Ms. Hutchinson or other officials that day. Ms. Hutchinson told the panel she recalled that on Jan. 6, Mr. Cipollone had opposed suggestions that Mr. Trump join a crowd on Capitol Hill pushing to overturn the election results. “We’re going to be charged with every crime imaginable,” Ms. Hutchinson recalled Mr. Cipollone saying. People familiar with the White House adviser’s schedule on Jan. 6, 2021, say he arrived at the White House late, though it was unclear exactly when. According to Ms. Hutchinson, Mr. Cipollone urged Mr. Meadows to do more to persuade Mr. Trump to withdraw the rioters. Ms. Hutchinson also told investigators that she had heard lawyers from the White House Counsel’s Office say that a plan to put Trump on the ballot in states won by Joseph R. Biden Jr. was not “legally sound.” Members of the House committee had hoped Mr. Cipollone would testify publicly at an earlier hearing, but he declined. They then went public with their case. From the hearing room, Representative Liz Cheney, R-Wyoming, singled out the former White House adviser by name, saying: “Our committee is certain that Donald Trump does not want Mr. Cipollone to testify here. But we believe the American people deserve to hear from Mr. Cipollone in person.”

Key revelations from the January 6 hearings

Any damaging report by Mr. Cipollone about Mr. Trump’s post-election actions would be a significant change from the president’s first impeachment trial, when Mr. Cipollone was his lead defender. In the first impeachment, Mr. Cipollone accused Representative Adam B. Schiff, the California Democrat who served as a prosecutor in that trial and now sits on the Jan. 6 panel, of making false allegations against Mr. Trump. A year later, as the president pressed ahead with plans to try to overturn his defeat, Mr. Cipollone and other White House lawyers repeatedly threatened to quit if Mr. Trump moved forward with some of the more extreme proposals, ultimately convincing him to retreat. Jared Kushner, Trump’s son-in-law and a former White House adviser, told the panel that threats to resign by Mr. Cipollone were frequent, implying that he did not take his and other members of his office’s concerns seriously. of Mr. Trump’s plans. “He and the team always said, ‘Oh, we’re going to quit. We won’t be here if that happens, if that happens,” Mr. Kushner said in videotaped testimony, an excerpt of which was played during the first public hearing. “So I took it as whining.”