US President Donald Trump announces his intent to nominate Mark Esper as US Secretary of Defense, White House said on Friday.

(File Photo: AP)

Esper is currently serving as the Secretary of the Army and previously served as a Vice President for Government Relations at the Raytheon Company, a major US defense contractor, the White House said.

The nomination of Esper was announced hours after Trump revealed he had come close to authorizing a strike on Iran after it shot down an American drone.

There hasn't been a full defense secretary since the resignation of James Mattis in December last year after splits in the administration over Trump's sudden decision to remove US troops from Syria.

Esper, who must be confirmed by the Senate, is the third man to lead the Pentagon in six months. 

He replaces Patrick Shanahan, who also led the military in an acting capacity but this week withdrew his name from consideration for defense secretary after facing questions over his past personal life and an allegation of domestic violence.

(With input from AFP)