U.S. Attorney General Jeff Sessions' involvement in the firing of former FBI Director James Comey may fall under the special counsel investigation into alleged ties between the Trump campaign and Russia, the Associated Press reported Friday.

Sessions wrote a letter to Trump last month arguing that "a fresh start is needed at the leadership of the FBI," and Comey was abruptly fired that same day. Sessions' deputy, Rod Rosenstein, also wrote a letter to the president advocating for Comey's termination, in part because he mishandled the investigation into Hillary Clinton's private server.

Robert Mueller, the former head of the FBI under Presidents George W. Bush and Barack Obama, was appointed last month as special counsel over the Russia investigation by Sessions's Justice Department.

While Mueller was initially overseeing the investigation into potential collusion between the Trump campaign and Russia, his probe has since expanded to allegations involving former Trump campaign manager Paul Manafort's contact with the Russians.

In an interview with the AP, Rosenstein said Mueller could include the Sessions matter in his investigation.

"The order is pretty clear," Rosenstein said. "It gives him authority for the investigation and anything arising out of that investigation, and so Director Mueller will be responsible in the first instance for determining what he believes falls into that mandate."

Rosenstein, who appointed Mueller special counsel, said he would recuse himself from anything matters that Mueller wants to include in his investigation.

"I've talked with Director Mueller about this," he told the AP. "He's going to make the appropriate decisions, and if anything that I did winds up being relevant to his investigation then, as Director Mueller and I discussed, if there's a need from me to recuse I will."