Trump is expected to relocate the base from Colorado to Alabama following a bitter, years-long battle between the two states over which should host the facility.

Democrat Biden had decided to keep Space Command -- which oversees US operations in outer space -- at its temporary location in Colorado despite a ruling by Republican Trump in his first term in 2021 that it should move to Alabama.

Colorado, in the western US, leans Democrat while the southern state of Alabama leans Republican.

White House Press Secretary Karoline Leavitt said in a statement sent to AFP that Trump "will be making an exciting announcement related to the Department of Defense" but gave no more details.

Trump is due to speak from the Oval Office at 2:00 pm (1800 GMT) in his first official public appearance for a week.

The Department of Defense's image distribution website initially listed Trump's announcement as being about "US Space Command Headquarters."

It later changed it to say only that "President Trump makes an announcement."

Speculation around Trump's announcement had earlier centered on his recent statements that he wanted to change the name of the Department of Defense to the Department of War.