The Trump transition team is discussing keeping Deputy Defense Secretary Robert O. Work in his current position for at least three to six months in the new administration as it builds a team of senior officials around defense secretary nominee James N. Mattis, according to three people familiar with the discussions.

The move would serve as a stopgap measure that creates continuity at the Pentagon, the people said, speaking on the condition of anonymity to discuss private deliberations. The decision is considered “all but a done deal,” according to one of the people familiar with the discussions. It also would keep Work in the job while the Pentagon prepares its first budget of the Trump administration.

Virtually all political appointees from the Obama administration are expected to leave their Defense Department jobs within days, including Army Secretary Eric Fanning, Navy Secretary Ray Mabus and Air Force Secretary Deborah James. The transition team has not announced nominees for several influential positions, including Navy secretary, Air Force secretary and undersecretary for policy. Trump last month nominated Vincent Viola, an Army veteran who became a billionaire after founding an electronic trading firm, for Army secretary.

A spokesman for Work in the Pentagon referred comment to the Trump transition team. Sean Spicer, the incoming White House press secretary, said Monday in an email that he has “made it clear that no decisions have been finalized/announced” for deputy defense secretary. He declined to answer whether Work has been asked to stay in his current position.

A Fox News journalist first tweeted the news Monday evening, shortly before The Washington Post published this report.

The Trump transition team has maintained that it is on track and ahead of schedule to assemble “the most qualified cabinet and administration in history.”

Mattis, who retired as the four-star chief of U.S. Central Command in 2013, is said to have rejected several candidates put forth by the Trump transition team and to have expressed interest in appointing some senior defense officials who were part of the Obama administration.

General James Mattis has been confirmed as secretary of defense (Jenny Starrs/The Washington Post)

Among them were Michèle Flournoy, who is currently the chief executive officer of the Center for a New American Security (CNAS) and the former undersecretary for policy under Obama. Flournoy was considered a front-runner to become defense secretary if Hillary Clinton had become president. Mattis, who was a member of the CNAS think tank’s board of directors until recently, expressed interest in making Flournoy deputy defense secretary, but she declined, privately citing differences of opinion with Trump, people familiar with the process said.

“Given recent media speculation, we wanted to clarify Michèle Flournoy will remain as CEO of CNAS, a position in which she has exceeded our highest expectations,” said Kurt Campbell, the chairman of CNAS’s board of directors, in a statement after Flournoy reached her decision. “She has the utmost respect for General Mattis. While she had several conversations with General Mattis about how she could support his success as the nominee for Secretary of Defense, she has no plans to return to government service at this time.”

Mattis has clashed with the Trump teams over who should be considered for jobs, according to a report Friday by a Washington Post columnist. The process allegedly became contentious after Mattis learned through media reports that Trump had picked Viola for Army secretary.

Similar conflicts have been underway in the State Department transition, where a series of officials have been considered and apparently rejected as deputy to secretary of state nominee Rex Tillerson.

Work, who turns 64 this month, has been deputy defense secretary since spring 2014. He previously served as chief executive of CNAS before Flournoy and as the undersecretary of the Navy under Obama.

Work would add to the list of Marines in Trump’s administration. A retired colonel, he served 27 years as a field artillery officer before leaving active duty in 2001. He became an influential Washington defense analyst, serving as a senior official with the Center for Strategic and Budgetary Assessments.

Under Defense Secretary Ashton B. Carter, Work has managed many of the day-to-day operations of the Pentagon and has been a chief architect of the “Third Offset Strategy,” a broad effort to ensure that the U.S. military keeps a competitive advantage on the battlefield by incorporating technology in creative ways.