Updated at 8 p.m. ET

The Senate Judiciary Committee on Tuesday rescinded subpoenas for two key witnesses in the Russia imbroglio, including President Trump's former campaign chairman, as part of agreements in which they'd agree to talk with the committee behind closed doors.

Former campaign boss Paul Manafort and Glenn Simpson, founder of the political research shop Fusion GPS, had been officially compelled to appear at an open hearing scheduled for Wednesday. Senate Judiciary Committee Chairman Chuck Grassley (R-Iowa) also wanted Donald Trump Jr. to appear.

But after issuing subpoenas for Manafort and Simpson after their attorneys suggested they didn't want to cooperate, Grassley said he was satisfied with the resulting negotiations. None of the three high profile figures are now expected to testify in the open session on Wednesday, although Grassley didn't rule out their doing so someday down the line.

"Our goal remains obtaining substantive information from witnesses to advance our oversight work and get answers the American people deserve," Grassley and ranking member Sen. Dianne Feinstein (D-Calif.) said in a statement.

Manafort met Tuesday morning with investigators from the Senate Intelligence Committee. Part of the issue with the Judiciary Committee's subpoena appeared to be a turf battle within the Senate.

Both committees are investigating aspects of Russia's attack on the 2016 presidential election. Manafort has become a central figure, as investigators look into whether the Trump campaign colluded with Russia in part because of Manafort's extensive pro-Russia connections.

Manafort was one of three top Trump campaign aides who attended a meeting in New York last year with a group of Russian advocates. Donald Trump Jr. had arranged the meeting in response to what his emails described as an offer of help from the Russian government with damaging information about Hillary Clinton.

Another Trump aide who attended, Trump's son-in-law and current senior White House adviser Jared Kushner, spoke to Senate Intelligence Committee investigators on Monday and was on Capitol Hill to speak with House Intelligence Committee staff members on Tuesday.

Simpson is the former Wall Street Journal reporter whose Fusion GPS research shop generated the infamous, unverified dossier about Trump that appeared early this year. The dossier, which has not been substantiated, purportedly was compiled by the Russian sources of a former British intelligence officer.

NPR correspondents Geoffery Bennett and Tamara Keith contributed to this report.

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