Deputy Attorney General Rod Rosenstein plans to leave Justice Department in mid-March: Official

Deputy Attorney General Rod Rosenstein has told colleagues he plans to leave the Justice Department in mid-March, according to a Justice Department official familiar with the matter.

Jeff Rosen, the current deputy at Transportation, is newly-confirmed Attorney General William Barr's top pick to become deputy attorney general, according to the official.

An announcement officially nominating a new deputy attorney general could come as early as this week, the official said.

In January, ABC News first reported that Rosenstein had communicated to President Donald Trump and White House officials his plan to depart the administration "in the coming weeks," around the time Barr would take office following a Senate confirmation, multiple sources said.

Sources told ABC News Rosenstein wanted to ensure a smooth transition to his successor and would accommodate the needs of Barr, should he be confirmed.

Barr was confirmed and sworn in on Feb. 14.

Rosenstein apparently had long been thinking he would serve about two years, and there was no indication that he was being forced out by the president.

Upon the termination of Attorney General Jeff Sessions, speculation mounted that Rosenstein would depart shortly thereafter, yet he's remained in his post as Matt Whitaker had served as acting attorney general since late November, until Barr's confirmation last week.

Rosenstein oversaw special counsel Robert Mueller's probe for more than a year, after Sessions had recused himself from the matter over his role in Trump's presidential campaign.

In May 2017, shortly after Trump fired James Comey as FBI Director, Rosenstein made the call to appoint Mueller to take over the FBI probe of Russia's meddling in the 2016 presidential election and any possible ties between Russian operatives and Trump associates.

Trump and his Republican allies have repeatedly blasted that decision.

Though Rosenstein became deputy attorney general under Trump, he served in senior Justice Department roles under both Republican and Democratic presidents. Many of his colleagues within the Justice Department view him as someone who's made decisions based on protecting the department's legacy.

From 2005 to 2017, Rosenstein served as U.S. attorney for the District of Maryland. Over 15 years before that, he served in senior roles throughout the Justice Department, prosecuting public corruption and other federal crimes, and serving as a senior counselor in the department during the Clinton administration.

During his March 2017 confirmation hearing to become deputy attorney general, Rosenstein told senators he would "certainly" resign his post if he felt he was being inappropriately pressured to influence an investigation.