Deputy Attorney General Rod Rosenstein is contemplating recusing himself from the FBI's investigation into Russia's interference in the 2016 election, according to a report.

Rosenstein has ultimate authority over special counsel Robert Mueller's Russia probe, which includes the possibility that President Trump tried to obstruct justice.

In a tweet, Trump confirmed Friday morning he is under investigation over his decision to fire FBI Director James Comey, and seemingly hinted at his displeasure with Rosenstein.

"I am being investigated for firing the FBI Director by the man who told me to fire the FBI Director! Witch Hunt," he said on his Twitter account.

Last month, Rosenstein outlined in a memo to Trump why he believed Comey should be fired, which Trump cited in his decision.

Rosenstein is serving as the acting attorney general for the investigation after Attorney General Jeff Sessions recused himself from the matter because of meetings he had with Russian officials.

ABC reports that Rosenstein knows he could become a witness in the investigation because of his role in Comey's firing. The news outlet said Rosenstein brought up the possibility of his recusal during a recent meeting with Associate Attorney General Rachel Brand, the Justice Department's third-in-command.

Brand would take over Rosenstein's responsibility in the Russia probe if he were to recuse himself.

Brand previously led the Justice Department's Office of Legal Policy and clerked for Supreme Court Justice Anthony Kennedy.

The ABC story comes the morning after Rosenstein raised eyebrows by releasing a statement condemning recent reports about Mueller's investigation.

"Americans should exercise caution before accepting as true and stories attributed to anonymous 'officials,' " Rosenstein said. "Americans should be skeptical about anonymous allegations. The Department of Justice has a long-established policy to neither confirm nor deny such allegations."