Longtime Trump confidant Roger Stone sent a letter to U.S. Attorney John Durham this week seeking answers about whether he was a subject of surveillance by the U.S. government.

"We have strong reason to believe that Mr. Stone was among three advisors to candidate Trump who was under surveillance by the FBI during the 2016 presidential campaign," Stone's lawyer Paul Jensen wrote in the letter obtained by The Hill. Jensen also said Stone's Fourth Amendment rights may have been violated.

Durham has been tasked by Attorney General William Barr with reviewing the origins of the counterintelligence investigation into President Trump's campaign.

Jensen cited a January 2017 New York Times article titled "Wiretapped data used in probe of Trump aides," which names Stone as one of at least three Trump campaign associates under scrutiny by American law enforcement and intelligence agencies. The other two were Trump campaign manager Paul Manafort and onetime Trump campaign adviser Carter Page.

Jensen also sent letters, dated May 20, to House Intelligence Committee ranking member Devin Nunes, R-Calif., and Senate Judiciary Committee Chairman Lindsey Graham, R-S.C.

The correspondence said Stone has reached out to the White House counsel to urge Trump to declassify documents related to the Russia investigation. If these records from the Justice Department and FBI are not released, Jensen said he would resort to suing the federal government.

According to Rep. Mark Meadows, R-N.C., a close ally of Trump, the declassification of Russia investigation documents are "right around the corner." In what appeared to be a nod of approval, Trump retweeted a Washington Examiner article of Meadows' comment on Wednesday.

Stone was arrested at his Florida home on Jan. 25 in a pre-dawn raid by the FBI. He was later charged by special counsel Robert Mueller with lying to Congress, witness tampering, and obstructing justice. Stone was released on a $250,000 bond and has pleaded not guilty. He is set to go on trial starting Nov. 5.