Senator Lindsey Graham is preparing to invite former special counsel Robert Mueller to testify before a Senate panel about the investigation into Russian interference in the 2016 election.
Mr Graham of South Carolina is chairman of the Senate judiciary committee.
He tweeted earlier that he would grant a 2019 request by Democrats on the panel for Mr Mueller to appear.
Mr Graham has been hinting at the move for some time as a way to grill Mr Mueller about the origins of the Russian investigation and what many Republicans regard as bias against US President Donald Trump by law enforcement agencies.
Two days earlier Mr Graham described the Mueller investigation as “biased and corrupt".
He finally acted after the publication on Saturday of an opinion piece in The Washington Post, in which Mr Mueller defended his work against "broad claims that our investigation was illegitimate and our motives were improper".
Mr Mueller wrote that former campaign aide Roger Stone, whose sentence was commuted by Mr Trump on Friday, “remains a convicted felon, and rightly so".
The comments were a rarity since Mr Mueller was chosen to oversee the Russia probe in 2017, and departed as special counsel in 2019 after the investigation was complete.
“Apparently Mr Mueller is willing and also capable of defending the Mueller investigation,” Mr Graham, who is up for re-election this year, tweeted on Sunday.
On Friday he tweeted that Mr Trump was justified in commuting Stone’s 40-month prison sentence, and that “over time we learn how biased and corrupt Crossfire Hurricane and the Mueller probes were".
Crossfire Hurricane was the code name for the investigation by the FBI in 2016 and 2017 into links between Russia and Trump associates.
Democrats on the Senate judiciary panel wrote to Mr Graham in May 2019 asking for Mr Mueller to testify on his report.
g there were “at least 60 unanswered questions” they hoped the former FBI director could address.