WASHINGTON — Deputy Attorney General Rod Rosenstein, who had been overseeing the special counsel investigation, plans to step down after Robert Mueller finishes his work, according to administration officials familiar with his thinking.

A source close to Rosenstein said he intends to stay on until Mueller's investigative and prosecutorial work is done. The source said that would mean Rosenstein would remain until early March. Several legal sources have said they expect the Mueller team to conclude its work by mid-to-late February, although they said that timeline could change based on unforeseen investigative developments.

The source said once Mueller's work is done, the special counsel's report to the Justice Department would follow a few weeks later, and Rosenstein would likely be gone by then.

But others familiar with his thinking said there’s no firm timeline and that Rosenstein would work out a departure plan once the new attorney general is confirmed and on board.

Rosenstein had long intended to serve about two years as the Justice Department's No. 2 official, the administration officials say. They add that this is his own plan and that he is not being forced out by the White House. That's despite the fact that he's been a frequent target of criticism from President Donald Trump on Twitter.

The administration officials had said that Rosenstein planned to remain on the job until a new attorney general is confirmed. After pushing out Jeff Sessions in November, Trump nominated William Barr, who planned to be at the Capitol on Wednesday to begin a round of courtesy calls with senators ahead of his confirmation hearing, which begins Jan. 15.

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White House press secretary Sarah Sanders said Wednesday on Fox News: "I know the deputy attorney general has always planned to roughly stay around two years. My guess is that he is making room for the new attorney general to build a team that he wants around him."

Rosenstein's intentions were first reported by ABC News. He did not respond to questions Wednesday morning.

Rosenstein considered resigning last fall, after a report surfaced that he had advocated secretly recording Trump, but he decided to stay on the job. Aides said he made a comment about having someone "wear a wire" around the president as a joke during a meeting.

Rosenstein had been overseeing the Mueller's investigation into possible Trump campaign collusion with Russia and obstruction of justice because Sessions recused himself because of his role in the Trump campaign. And even with the arrival of acting Attorney General Matt Whitaker, who took over the probe, Rosenstein has continued to help supervise it.

If Barr is confirmed, as seems likely, he will fully take over the investigation. Several legal sources have said it appears that the Mueller investigation is entering its final stages. But Barr would play a key role in deciding whether and how to share Mueller's expected report with Congress and whether to make all or part of it public.

Responding to news of Rosenstein's impending departure, Democratic Sen. Tim Kaine of Virginia told CNN's "New Day" that he has "deep concern" about how Barr will handle the Mueller probe. He referred to a memo Barr wrote in which he was critical of the investigation.

"William Barr was sending freelance memos to the Trump administration making a case to undercut the Mueller investigation," Kaine said. "So the deep concern will be if he comes in and Rosenstein is gone, is this just a preface to either undercutting the investigation or trying to keep the results of it hidden from the American public."

Rosenstein has been a consistent defender of Mueller and the Justice Department, responding to attacks from Republicans in Congress. He told a Law Day conference last May that the department "is not going to be extorted," after some House Republicans raised the prospect of seeking Rosenstein's impeachment.

The attacks from Congress and the White House were a jolt for Rosenstein, who enjoyed bipartisan support for most of his three decades as a federal prosecutor. But his congressional support faltered when he wrote a memo providing a rationale for Trump's decision to fire FBI Director James Comey.

By appointing Mueller to take over the Russia investigation as a special counsel, Rosenstein won back Democrats but angered the president, who tweeted, "I am being investigated for firing the FBI Director by the man who told me to fire the FBI Director! Witch Hunt."