Trump is expected to nominate acting Pentagon chief Mark Esper for Defense secretary

Mark Esper testifies before the Senate Armed Services Committee during his confirmation hearing to be secretary of the U.S. Army in the Dirksen Senate Office Building on Capitol Hill November 2, 2017 in Washington, DC.

Chip Somodevilla | Getty Images News | Getty Images

WASHINGTON — President Donald Trump is expected to nominate acting Defense Secretary Mark Esper to lead the Pentagon, three administration officials told NBC News.

Earlier in the week, Trump announced that he would not nominate acting Secretary of Defense Patrick Shanahan to take the top role in the Pentagon. Instead, Trump said Esper — who previously was Army secretary — would take over as acting Defense secretary.

Esper had widely been discussed as a possible replacement nominee. The Pentagon did not immediately respond to a request for comment.

Shanahan left the Pentagon on Friday to applause from the officials gathered outside the building. Esper will officially take over at midnight Sunday. 

Read more: Trump says Shanahan has withdrawn from Defense secretary consideration

Esper is a graduate of the U.S. Military Academy and served in the 1990-1991 Gulf War with the Army's 101st Airborne Division. Following active duty, he served in the Army Reserve and both the Virginia and District of Columbia National Guard before retiring in 2007.

Esper's ascension to the top spot in the Pentagon comes at a particularly tumultuous time.

Tensions with Iran have increased since the Trump administration withdrew from the 2015 Iran nuclear deal last year. On Thursday night, Trump ordered — then canceled — strikes on Iran after the Middle Eastern country downed an unmanned U.S. drone. On Friday, the president said he decided not to carry out the strikes after deciding the potential deaths from the attack would not be "proportionate" to losing the drone.

What's more, the Trump administration has pulled the United States back from global commitments and pushed forward on ambitious projects like the denuclearization of North Korea, a growing military footprint on the southwest border with Mexico and rising tensions in Venezuela.

Like Shanahan, Esper, if confirmed by the Senate, would head the largest federal agency with limited experience in foreign policy. Esper, a former Raytheon executive, left the defense giant to become the 23rd secretary of the U.S. Army in 2017.

Defense Department's Patrick Shanahan, before he was tapped by President Donald Trump to serve as the department's Acting Secretary

Department of Defense

Shanahan spent just over 30 years at one of the nation's top defense companies. People close to the former Boeing executive say his departure from the highest echelons of the corporate world was motivated by his father, a Vietnam War veteran and Bronze Star recipient.

Shanahan ascended to the acting role in the wake of former Defense chief Jim Mattis' shocking resignation in December. In his resignation letter, Mattis said that disagreements with the president about America's treatment of both allies and strategic competitors came from beliefs that "are strongly held and informed by over four decades of immersion in these issues."

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