WASHINGTON — Lev Parnas, the Soviet-born businessman who played a central role in the campaign to pressure Ukraine to investigate political rivals of President Trump, completed his break with the White House on Wednesday, asserting for the first time in public that the president was fully aware of the efforts to dig up damaging information on his behalf.

In an interview with The New York Times on the day the House transmitted articles of impeachment against Mr. Trump to the Senate, Mr. Parnas also expressed regret for having trusted Mr. Trump and Rudolph W. Giuliani, the president’s personal lawyer and the architect of the Ukraine pressure campaign. His lawyer said he was eager to cooperate with federal prosecutors investigating Mr. Giuliani.

Mr. Parnas made his remarks as House impeachment investigators released more material he had turned over to them. The material, including text messages, photos and calendar entries, underscored how deeply Mr. Parnas and others were involved in carrying out the pressure campaign and how new information continues to surface even as the Senate prepares to begin Mr. Trump’s trial next week. And it provided additional evidence that the effort to win political advantage for Mr. Trump was widely known among his allies, showing that Mr. Parnas communicated regularly with two top Republican fund-raisers about what he was up to.

Text messages and call logs show that Mr. Parnas was in contact with Tom Hicks Jr., a donor and Trump family friend, and Joseph Ahearn, who raised money for pro-Trump political groups, about developments in the Ukraine pressure campaign.