Washington (CNN) Former Trump campaign adviser George Papadopoulos testified to Congress that the FBI had asked him to wear a wire in 2017 to record his conversations with a professor who had ties to Russia and claimed that Russia had dirt on Hillary Clinton in the form of stolen emails.

Papadopoulos rejected the FBI's request to wear a wire, he told lawmakers in October 2018, and he pleaded guilty in 2017 to lying to the FBI about his contacts with the professor, Joseph Mifsud, who remains one of the mysterious figures in the Russia investigation.

The new details about Papadopoulos and the FBI's request for a wire were disclosed Tuesday as Papadopoulos raised new questions about his plea agreement with special counsel Robert Mueller and openly said he would accept a pardon from Trump.

Papadopoulos has released a new book, titled "Deep State Target," in which he claims that he did not actually lie to the FBI about his contacts with Mifsud, but rather was pressured into a plea agreement by Mueller's team.

Mueller, in Papadopoulos' court proceedings, said Papadopoulos' lies to the FBI in early 2017 were intentional and hurt the agency's ability to question, detain or arrest Mifsud when he was in Washington, DC, around that time.

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