While the department's official name is set in law, Trump in an executive order is authorizing use of the new label as a "secondary title" by his administration, a White House document said.

Defense officials are permitted to use to use "secondary titles such as 'Secretary of War,'...in official correspondence, public communications, ceremonial contexts, and non-statutory documents within the executive branch," according to the document.

It was not immediately clear when Trump planned to sign the order, but his public schedule for Friday said he would be signing executive orders in the afternoon as well as making an announcement in the Oval Office.

The president, a marketing-savvy real estate developer, has repeatedly said in recent weeks that he was mulling such a change.

Late last month, the 79-year-old Republican claimed the Defense 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.

According to the White House document, the name change "conveys a stronger message of readiness and resolve."

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.

"Restoring the name 'Department of War' will sharpen the focus of this Department on our national interest and signal to adversaries America's readiness to wage war to secure its interests," the White House document said.

The move is the latest overhaul at the Pentagon since Trump took office in January and appointed former Fox News host Pete Hegseth to lead the sprawling department.

Hegseth, a combat veteran, has repeatedly touted the push to restore a "warrior ethos" in the department, and has lambasted prior administrations for policies he and Trump have derided as "woke."

Hegseth notably has sought to expel transgender troops from the military and change the names of bases that honored Confederate troops back to their original titles, after they were renamed under former president Joe Biden.

While Trump's order could potentially be rescinded by a future president, it "instructs the Secretary of War to recommend actions, to include legislative and executive actions, required to permanently rename"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.