The Pentagon's chief spokesman is leaving as Ash Carter takes over as the new defense secretary.

Navy Rear Adm. John Kirby acknowledged on Wednesday that he will be stepping down after having served as press secretary during the tenure of Chuck Hagel, who resigned under pressure from the White House.

Carter, who was sworn in on Tuesday, has made it known that he wants a civilian in the position of Pentagon spokesman.

Kirby, who has served as a Navy officer since 1986, said the timing of his departure has not been settled.