These are the top names in contention for defense secretary under Trump

National security minds in Washington, D.C., are awaiting President-elect Donald Trump's decision for defense secretary.

Trump's pick of Rep. Michael Waltz, R-Fla., as his national security adviser and his expected pick of Sen. Marco Rubio, R-Fla., for secretary of state, set a tone for his foreign policy that is expected to be hawkish on China and Iran. 

Whoever Trump picks for defense secretary will oversee major changes within the Pentagon, both a reorienting of troop posture abroad and an across-the-board stripping of DEI provisions they believe caused the Pentagon to go "woke" under President Biden. 

A litany of names has been tossed around for who could lead the government’s largest agency, with one running theme: while his pick needs to pass a Senate confirmation, Trump is expected to appoint a loyalist who will not undermine him. 

During his first term, five men held the job as Pentagon chief only to resign, be fired or serve briefly as a stopgap.

"I don't think [Trump] really knows yet who he wants for defense secretary," one source familiar with the transition process said. "I don't think he's decided."

One possibility is Robert Wilkie, Trump’s former Veterans’ Affairs secretary. Prior to his VA confirmation in 2018, he served as undersecretary of defense for personnel and readiness under Trump and served in both the Navy and Air Force Reserve. Wilkie has been leading the Trump transition team with Pentagon staffing. 

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Wilkie is a fellow at the Trump-aligned America First Policy Institute and a military analyst for Newsmax. 

Another name is Robert O’Brien, Trump’s former national security adviser who has also been involved with the transition team. O’Brien told Fox News Digital that "of course" he would return to a Trump administration. 

O’Brien has been outspoken about the need to pivot U.S. defenses to China. He said the way to force Russia to the negotiating table with Ukraine was through steeper sanctions – and bringing Ukraine into NATO "risks World War III." 

Richard Grenell, Trump’s former acting director of national intelligence and German ambassador, was also expected to land a national security role in this administration. With the state and national security adviser roles filled, he, too, could land at the Department of Defense. 

Throughout the campaign, Grenell advised Trump on foreign policy and political issues, and led outreach to Arab Americans in Michigan. He appeared with Trump in September when he met with Ukrainian President Volodymyr Zelenskyy.

Grenell was a pro-Trump antagonist to Europe during his time in Germany, with the former president joking about former German Chancellor Angela Merkel's happiness when Grenell was moved to the national security role. 

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Sen. Joni Ernst, the defense-minded Iowa Republican and current GOP conference chair, has also been floated as a possibility, a source confirmed to Fox News Digital, but she remains "laser-focused" on her GOP conference chair race. She also served in the Army Reserve and Iowa Army National Guard. 

If picked, she would be the first female defense secretary. 

Rep. Mike Rogers, R-Ala., head of the House Armed Services Committee, was also under consideration and has been contacted by the transition team, a source familiar confirmed. 

However, two sources said that Trump is likely to pull from the private sector for this role. Picking from Congress would whittle away narrow GOP majorities in those chambers, at least until seats were filled. 

Rogers is also a staunch supporter of aiding Ukraine – a position that might put him at odds with Trump. 

Retired Lt. Gen. Keith Kellogg, who held high-level national security posts during Trump’s first term, has also been named as a possibility. 

"The president is going to make the call on who is in his administration," Kellogg recently told Fox News Radio's Guy Benson, while suggesting he would say yes if the president called. "It's going to be a very loyal team." 

Sen. Tom Cotton, R-Ark., had been a lead contender for an administration role, likely defense secretary or CIA head, but pulled his name from the running, a source confirmed. He is running for Republican Conference chair and is likely to take over Rubio’s position as head of the Intelligence Committee.

Former Secretary of State Mike Pompeo had been floated, but on Saturday, Trump posted on Truth Social that Pompeo would not be joining this administration – and neither would former United Nations Ambassador Nikki Haley. 

Fox News' Liz Elkind contributed to this report.