WASHINGTON – Deputy Attorney General Rod Rosenstein, who oversees the special counsel investigation into the 2016 election, is expected to leave his post in a matter of weeks, a person familiar with the matter said Wednesday.

The move is timed to the anticipated confirmation of William Barr, who was nominated by President Donald Trump to succeed ousted Attorney General Jeff Sessions.

The person familiar with the transition said Rosenstein is leaving on his own terms.

Senate confirmation hearings for Barr are scheduled to start Jan. 15, and a vote could follow in the coming weeks.

Rosenstein's departure would come after a tumultuous 20 months, in which he has often been placed at odds with the administration he works for and Trump himself.

Since his appointment of Robert Mueller to lead the Justice Department’s investigation of Russian interference in the 2016 election, Rosenstein has been the target of unrelenting criticism from Trump, who derided the inquiry as a witch hunt.

Rosenstein has been a shield for Mueller as Trump and some Republican lawmakers mulled removing them both.

Rosenstein’s appointment of Mueller was prompted by Sessions’ recusal from the inquiry because of his work for the Trump campaign. The recusal led to Sessions’ firing after the midterm elections in November.

If confirmed, Barr would assume management of the Mueller investigation, which may be in its final stages. Rosenstein has helped oversee the inquiry since the appointment in November of acting Attorney General Matthew Whitaker, the interim replacement for Sessions.

Barr was on Capitol Hill Wednesday, meeting with lawmakers before next week's hearing before the Senate Judiciary Committee. Barr served as attorney general from 1991 to 1993 during the administration of President George H.W. Bush.

Asked about Rosenstein's status, White House spokeswoman Sarah Sanders said Wednesday that the deputy attorney general had long planned to serve two years. He was confirmed by the Senate April 2017.

"I know (Rosenstein) has a great deal of respect for the new nominee for attorney general, Mr. Barr," Sanders said on Fox News. "And I think they have a great relationship.

"I haven't spoken to the deputy attorney general myself, so I'll leave any announcement for him or the president to make when they want to do that. But certainly, I don't think there's any willingness by the president or White House to push him out. My guess is that he is making room for the new attorney general to build a team he wants around him."

Rosenstein had considered resigning from his post as recently as September in the wake of a New York Times report indicating that the deputy attorney general suggested invoking the 25th Amendment last year to remove Trump.

Rosenstein strongly denied the report, which indicated that he suggested recording Trump's conversations in hopes of triggering the president's removal from office.

A career attorney at Justice before taking the No. 2 post in April 2017, Rosenstein's tenure has been inextricably joined with the Russia investigation.

Less than a month after his confirmation, he wrote a controversial memo supporting the removal of FBI Director James Comey.

Trump's dismissal of Comey is being examined by Mueller as part of his inquiry into whether the president sought to obstruct the Russia investigation.

Rosenstein announced the appointment of Mueller shortly after.

Democrats, who have unsuccessfully sought to pass legislation to protect Mueller from any attempt by the White House to remove him, expressed deep concern Wednesday after learning of Rosenstein's pending departure.

Senate Minority Leader Charles Schumer, D-N.Y., said the development at Justice "heightens the stakes" for Barr's looming confirmation hearing.

Schumer cited a memo Barr sent to Justice last year that was critical of the Russia inquiry.

"From all accounts, Mr. Rosenstein has been an impartial actor at the head of the special counsel's investigation," Schumer said.

Sen. Dick Durbin of Illinois, the assistant Democratic leader and a member of the Judiciary Committee, said Wednesday he is concerned about Barr protecting the Mueller investigation.

“I’m concerned when this man, who has a good reputation as a lawyer and professional, volunteers to the Trump administration that they should constrain Mueller’s investigation,” Durbin said. “This is not a good starting point for someone who as attorney general would have supervisory authority over the investigation.”

Sen. Lindsey Graham, R-S.C., a member of the Judiciary Committee who met with Barr Wednesday, said the nominee was "committed to allowing Mr. Mueller to finish" his work.

Rosenstein strongly supported Barr's nomination and said the Russia inquiry was proceeding as it should.

The deputy attorney general joined the department in 1990 through the attorney general’s honors program.

During independent counsel Kenneth Starr’s investigation of President Bill Clinton, Rosenstein helped convict three associates of the Clintons – Susan McDougal, James McDougal and former Arkansas Gov. Jim Guy Tucker – on fraud and conspiracy charges in May 1996.

Rosenstein became an assistant U.S. attorney in Maryland, prosecuting federal court cases and arguing appeals at the 4th U.S. Circuit Court of Appeals. He served four years in the Justice Department’s tax division.

He served 12 years as U.S. attorney for Maryland before beginning his stint as deputy attorney general.