(CNN) George Papadopoulos testified Thursday for seven hours before the House Judiciary and Oversight Committees , but he is seeking immunity before he agrees to speak to a different congressional committee, two sources familiar with the matter told CNN.

Papadopoulos has requested immunity in exchange for his testimony before the Senate Intelligence Committee, the sources say, which is conducting an investigation into 2016 Russian election meddling.

Papadopoulos, the former Trump campaign adviser who pleaded guilty to lying to the FBI , did not have immunity or limits on his testimony when he voluntarily appeared before the two House panels on Thursday, although his lawyer was able to object to questions, according to two sources familiar with his House interview.

The House and Senate investigations, of course, have a different aim: the Senate Intelligence Committee is investigating Russian meddling and possible collusion during the 2016 election, while the House panels are investigating the FBI and Justice Department's handling of investigations into Hillary Clinton and Russia.

Papadopoulos is a key figure to both investigations because of his role sparking the FBI's counterintelligence investigation into Trump and Russia, which began in July 2016 when Australian diplomat Alexander Downer reported to the FBI that Papadopoulos told him about Russian dirt on Clinton.

It's not yet clear how Papadopoulos' House testimony will impact his negotiations with the Senate panel, which are still ongoing, according to two sources.

If Papadopoulos does not voluntarily agree to testify, the committee has the ability to subpoena him.

Under a subpoena, Papadopoulos could assert Fifth Amendment rights to not answer questions, although the committee could also reject those claims, including by citing his prior testimony. That's what happened several years ago when the House Oversight Committee held IRS official Lois Lerner in contempt , asserting she waived her Fifth Amendment rights by making a statement to the committee.

"The committee may choose to reject the witness's privilege assertion, essentially determining that the privilege does not apply to the type of testimony or documents sought from the witness, or, as in the case of former Internal Revenue Service official Lois Lerner, that the witness has waived her Fifth Amendment rights," the Congressional Research Service wrote last year.

Papadopoulos' attorney, Caroline Polisi, declined to comment on the immunity request.

Papadopoulos was sentenced to 14 days in prison last month for lying to the FBI about his interactions with Maltese professor Joseph Mifsud, who told Papadopoulos in 2016 that Russians had dirt on Hillary Clinton. But since his sentencing, which he has yet to serve, Papadopoulos has become more outspoken claiming that Mifsud was setting him up with a meeting arranged by British and Australian intelligence agencies.

Papadopoulos appeared even more emboldened following Thursday's interview, suggesting in a Fox News interview Friday he's considering withdrawing from his plea agreement, although it's not clear that would even be possible since he was already sentenced in September and has agreed to waive many of his rights in the federal court system.

"I believe there was tremendous misconduct on the government's behalf regarding my case," Papadopoulos told Fox News. "And given certain information I learned just yesterday that I can't publicly disclose right now, I'm considering withdrawing my agreement with the government."

Polisi said there were "a number of options on the table right now and we are evaluating all of them closely."

Papadopoulos also provided some information to special counsel Robert Mueller as part of his decision to plea, but his cooperation with the special counsel was limited and was never "substantial," prosecutors have said.

The Republican lawmakers who attended Thursday's House interview would not say that Papadopoulos provided evidence to corroborate his claims about being set up.

But they have asserted that the FBI and the Justice Department took troubling steps in the Russia investigation, particularly their reliance on the opposition research dossier on Trump and Russia to obtain a foreign surveillance warrant on former Trump adviser Carter Page. Republicans are also raising questions after Thursday's interview about the start of the probe.

"The facts that we're finding in here are astounding that we would allow this type of investigation to be embarked upon without any real solid foundation of collusion," Rep. Mark Meadows, a North Carolina Republican, said following Thursday's interview.

Ahead of Papadopoulos' testimony, Polisi sent the House Committees a letter with nine names Papadopoulos was prepared to testify about, including Downer and Mifsud. But he declined to answer questions on other topics, including statements he made included in his plea agreement and charging documents from Mueller, according to a source familiar with his testimony.

In the Senate, Intelligence Chairman Richard Burr has said his committee has yet to find any hard evidence of collusion between Trump's team and Russia. But Burr has also made clear their investigation isn't finished yet, and he's said there are several key witnesses the panel still needs to speak to.

Papadopoulos isn't the first witness to request immunity from Congress in connection to the Russia investigations: Former Trump National Security Adviser Michael Flynn, who also pleaded guilty to lying to the FBI last year, had earlier sought immunity protections in March 2017.

Flynn's immunity request was rejected, and he has not spoken to the Senate committee or any other congressional panels while his cooperation agreement with Mueller remains in effect.