WASHINGTON — Paul Manafort, who served as a top aide to President Trump’s 2016 campaign, on Tuesday provided congressional investigators notes he took during a Trump Tower meeting with a Russian lawyer that has emerged as a focus in the investigation of Russian interference in the election.

Manafort’s submission, which came as he was interviewed in a closed session by staff members for the Senate Intelligence Committee, could offer a key contemporaneous account of the June 2016 session, which was organized by the president’s oldest son and has gained attention in recent days from lawmakers as well as special counsel Robert S. Mueller III.

The notes were not publicly disclosed, and representatives for Manafort declined to comment on their contents.

Manafort’s testimony had been widely anticipated but took place without prior announcement early Tuesday, hours before senior White House adviser Jared Kushner appeared on Capitol Hill to meet with the House Intelligence Committee.

Kushner had met with the Senate committee a day earlier and delivered a public statement insisting that he did not collude with the Russian government while working as a campaign adviser to his father-in-law, the president.

Manafort’s interview centered on the Trump Tower meeting, in which he met with Kushner, Donald Trump Jr., a Russian lawyer and others, according to a person familiar with the committee session who was not authorized to discuss the matter publicly.

Manafort’s lawyers have agreed to make him available to speak with Senate Intelligence Committee staffers and members in the future to discuss other issues, the person said.

Jason Maloni, a Manafort spokesman, said Manafort met “with the bipartisan staff of the Senate Intelligence Committee and answered their questions fully.”

Manafort’s appearance came as he has been engaged in intense negotiations with congressional committees about how and when to provide testimony.

Late Tuesday, the Senate Judiciary Committee announced it had withdrawn a subpoena that had been issued to compel Manafort to appear Wednesday.

In a joint statement, committee chairman Sen. Charles Grassley, R-Iowa, and the committee’s top Democrat, Sen. Dianne Feinstein, California, said Manafort has begun producing documents to the committee and that negotiations will continue over a possible interview at a future date.

“Our investigation is still in its early stages, and we will continue to seek information from witnesses as necessary,” the statement said. “As we’ve said before, we intend to get the answers that we need, one way or the other.”

They indicated the committee could seek to compel Manafort’s testimony at some point in the future.

The developments Tuesday were a sign that investigations are gathering momentum in front of multiple congressional committees.

Ben Rhodes, an adviser to President Obama, confirmed that he was also interviewed by Senate Intelligence Committee staff on Tuesday.

And Grassley and Feinstein announced that they had reached an arrangement with another witness they had subpoenaed to appear Wednesday: Glenn Simpson, the co-founder of Fusion GPS, a firm behind a dossier written during the campaign that included salacious but unverified information linking Trump to Russia. Trump has vigorously denied the dossier’s allegations.

Simpson initially said through his lawyer that he would invoke his Fifth Amendment right against self-incrimination if forced to appear. But on Tuesday, he agreed to a transcribed interview behind closed doors, Grassley and Feinstein said. A lawyer for Simpson, Joshua Levy, declined to comment.

Simpson and Manafort were initially slated to appear on the same panel along with Trump Jr. at Wednesday’s hearing, where lawmakers were expected to ask the Trump surrogates about the June 2016 Trump Tower meeting.

Emails sent to Trump Jr. before the meeting show he agreed to meet with Russian attorney Natalia Veselnitskaya after being told she was a Russian government lawyer, bearing damaging information about Trump’s opponent, Hillary Clinton, that was being shared as part of a Russian government effort to help his father’s campaign.

Manafort’s notes could provide information about what, exactly, was said at the meeting and how participants responded. Manafort, who was a top adviser at the time of the meeting, was named campaign chairman days later.

In an initial statement as the New York Times prepared to report that the meeting had taken place, Trump Jr. had said it was “primarily” about the issue of the adoption of Russian children by U.S. families. The Russian government halted such adoptions in retaliation for a U.S. law passed in 2012 that blacklisted top Russian officials over alleged human rights abuses.

Later, Trump Jr. acknowledged that Veselnitskaya had first described information she believed could be damaging to Democrats but has called that information “vague” and “ambiguous.” Rinat Akhmetshin, a Russian American lobbyist who also attended the meeting, has said that Veselnitskaya left behind documents describing the information.

Manafort’s notes could shed more light on the information she provided and what happened to the documents she brought to the session.

The Washington Post’s Tom Hamburger and Ellen Nakashima contributed to this report.