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

WASHINGTON — The White House declined to comment Monday on whether acting Secretary of Defense Patrick Shanahan would be tapped later this week by President Donald Trump to take the top spot at the Pentagon.

"I'm not going to make any personnel announcements at this time," press secretary Sarah Huckabee Sanders told reporters Monday during a media briefing at the White House.

"I can tell you that the president has a great deal of respect for acting Defense Secretary Shanahan, he likes him, and when the president is ready to make an announcement on that front, he certainly will," Sanders said.

Shanahan ascended to the acting role in the wake of then-Secretary of Defense James Mattis' shock 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."

Mattis, a revered Marine with a military career spanning four decades, was known for his battlefield prowess and kinship with rank-and-file service members. Before he became Trump's Defense secretary, the four-star general led the U.S. Central Command, the combatant command responsible for the wars in Iraq and Afghanistan.