President Donald Trump has announced that budget director Mick Mulvaney will be his next chief of staff.

Mr Trump tweeted on Friday that Mr Mulvaney “has done an outstanding job” in his administration and would take over next year.

Mr Trump deemed Mr Mulvaney his “acting chief of staff” but it was not immediately clear what that meant for the length of his tenure.

He will replace John Kelly.

Mr Trump praised Mr Kelly’s service and called him a “great patriot” in the tweet.

Mr Trump announced last week that Mr Kelly, who served in the post for more than a year, would soon be departing.

Trump Chief of StaffMick Mulvaney (Manuel Balce Ceneta/AP)

The president’s first choice was Nick Ayers, the vice president’s chief of staff, who bowed out after being unable to come to an agreement on how long he would serve in the post.

Journalist and TV presenter Piers Morgan had been among the names linked to the post which is effectively to act as the president’s gatekeeper.

Trump Chief of StaffPresident Donald Trump walks in to the Roosevelt Room with outgoing hief of staff John Kelly in the background (Susan Walsh/AP)

It comes as Mr Trump begins to focus his attention on seeking a second term in 2020 after voters delivered a mixed verdict in the midterm elections.

Candidates for the White House are expected to start throwing their hats into the ring in the new year.