US President Donald Trump is directing that the Department of Defence be known as the Department of War.

He will sign an executive order on Friday for the Defence Department to use the new name as a secondary title and for Defence Secretary Pete Hegseth to be known as Secretary of War.

The Pentagon - which oversees the US armed services - is the successor to the War Department, which was first established as a cabinet-level agency in 1789 and existed until 1947.

The responsibility of creating executive departments rests with the US Congress, meaning that an amendment would be required to change the department's name legally.

The BBC has seen the text of the executive order, which says: "The name 'Department of War' conveys a stronger message of readiness and resolve compared to 'Department of Defence,' which emphasises only defensive capabilities."

In an effort to "project strength and resolve," the order authorises the Defence Secretary, his department, and subordinate officials to use the new titles as secondary names.

The order also instructs Hegseth to recommend and include legislative and executive actions to move toward a permanent renaming of the department, since Trump cannot formally change the name without congressional approval.

The Department of War was established by George Washington but was rebranded following World War II.

According to the executive order, restoring its name "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 is yet to say how much a permanent rebrand would cost, but US media expects a billion-dollar price tag for the overhaul of hundreds of agencies, emblems, email addresses, uniforms and more, possibly hampering the Pentagon's efforts to cut spending and waste.

Trump has repeatedly floated the idea of the name change, arguing that the US had "an unbelievable history of victory" in both world wars under the previous name.

He has also expressed optimism that lawmakers would support such a change.

"I'm sure Congress will go along if we need that. I don't even think we need that," the president said last week. "But, if we need that, I'm sure Congress will go along."

Trump and Hegseth have sought to refocus the department on "warfighting" and a "warrior ethos".

They have argued that the department has become too focused on diversity, equity and inclusion programmes and "woke ideology".

Earlier on Thursday, Trump downplayed suggestions about seeking the Nobel Peace Prize.

"All I can do is put out wars," he told CBS News, the BBC's US partner. "I don't seek attention. I just want to save lives."

The renaming marks the president's 200th executive order signed since he took office.

Although the renaming was somewhat expected, it comes on the heels of China unveiling a range of new weapons, drones and other military hardware in a massive parade that many interpreted as a clear message to the US and its allies.