Trump will sign an executive order permitting use of the Department of War as a "secondary title" for the sprawling department, a White House document said, apparently due to its official name being set in law.

The name change "conveys a stronger message of readiness and resolve," the document said.

Trump in recent weeks has said several times that he wanted to make such a shift, claiming the department's title was too "defensive."

The Department of War "was the name when we won World War I, we won World War II, we won everything," he told reporters on August 25.

Established in the early days of US independence, the Department of War historically oversaw American land forces.

A government reorganization after World War II brought it along with the US Navy and Air Force under the unified National Military Establishment, which in 1949 was retitled to the Department of Defense.

Trump's order "instructs the Secretary of War to recommend actions, to include legislative and executive actions, required to permanently rename" the department, the White House document said.

Officials are nonetheless authorized to use "secondary titles...in official correspondence, public communications, ceremonial contexts, and non-statutory documents within the executive branch."