WASHINGTON — Paul Manafort, a top campaign aide to President Donald Trump, appeared before the Senate Intelligence Committee early Tuesday morning to answer questions about Russian interference in the 2016 presidential election.

Before his voluntary interview, Manafort submitted to the committee notes that he took at a meeting with a Russian lawyer he and other campaign aides attended during the presidential campaign, a person familiar with the investigation said.

The notes could provide a key contemporaneous account of a meeting that has emerged as a focus of investigations into Russia's interference in the 2016 campaign by both Congress and Special Counsel Robert Mueller.

Manafort's testimony had been widely anticipated but took place without prior announcement early Tuesday, hours before senior White House adviser Jared Kushner appeared before the House Intelligence Committee.

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

The Tuesday morning interview was held at the request of Manafort's legal team, specifically for the purpose of discussing the June 2016 meeting he participated in with Kushner, the president's son, Donald Trump, Jr., a Russian lawyer with purported Kremlin ties and others with various connections to Russia, according to a person familiar with the meeting. 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.

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

Despite his appearance before the Senate Intelligence Committee, the Senate Judiciary Committee has continued to press for him to appear separately and late Monday, the committee issued a subpoena compelling Manafort's appearance at a hearing on Wednesday.

In a joint statement, committee chairman Sen. Charles Grassley, R-Iowa, and its ranking Democrat, Sen. Dianne Feinstein of California, said negotiations over Manafort's voluntary cooperation broke down after Manafort's lawyer indicated he was willing to provide only one transcribed interview with congressional staff.

"While the Judiciary Committee was willing to cooperate on equal terms with any other committee to accommodate Mr. Manafort's request, ultimately that was not possible," they said.

Grassley and Feinstein said they were willing to continue talks to excuse Manafort from the hearing if he agreed to voluntarily provide documents and an interview to their committee.

"Paul has been cooperative from the beginning, and we are confident we can work something out," Maloni said.

On Tuesday, Grassley and Feinstein announced they had reached an arrangement with another witness they subpoenaed to appear Wednesday: Glenn Simpson of Fusion GPS, a firm behind a dossier filled with salacious but unverified details about time Trump spent in Moscow. Simpson initially said through his lawyer that he would invoke his Fifth Amendment right against self-incrimination if forced to testify, but agreed, according to Feinstein and Grassley, to a transcribed interview behind closed doors.

"We've reached an agreement on this request and have withdrawn the subpoena," Grassley and Feinstein said in a joint statement.

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 a June 2016 meeting they attended in Trump Tower with purported Russian operatives.

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 would be named the campaign's chairman days after the June 9, 2016 meeting, attended at Trump Jr.'s request, as did Trump's son-in-law Kushner.

In a statement Monday, Kushner said he has found an email he sent an assistant during the meeting, requesting that he be called on his cellphone to provide an excuse to leave early.

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 American families. The Russian government halted such adoptions in retaliation for a U.S. law passed in 2012 which blacklisted top Russian officials over alleged human rights abuses.

Later, he 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.

Trump has vigorously denied the allegations in the dossier, reports written during the campaign that outlined alleged connections between Trump and the Russian government. The firm, Fusion GPS, also conducted research work on behalf of a law firm working with a Russian client of Veselnitskaya, who had been sued by U.S. authorities in New York.

A lawyer for Simpson, Joshua Levy, declined to comment.

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