WASHINGTON DC — The Pentagon announced on Wednesday that Navy Secretary John C. Phelan is leaving his post effective immediately, with Navy Undersecretary Hung Cao stepping in as acting secretary. Pentagon officials did not offer a reason for the departure.

"Secretary of the Navy John C. Phelan is departing the administration, effective immediately," Pentagon spokesman Sean Parnell announced. "We wish him well in his future endeavors."

An anonymous source, as reported by Reuters, said Phelan had been fired by the Pentagon. The day before his departure, Phelan addressed sailors and industry professionals at the Navy's annual conference in Washington and spoke with reporters about his agenda.

Before joining the administration, Phelan ran a private investment firm. He is also among the country's top art collectors.

Cao, who will serve as acting secretary, is a Navy veteran and a former Virginia Senate candidate. Reports have indicated that President Trump has expressed positive regard for Cao, though that characterization has not been independently confirmed at high confidence.

The departure comes as Defense Secretary Pete Hegseth has made several leadership changes across the military. Hegseth fired the Army's top officer, General Randy George, weeks before Phelan's departure. Since taking office last year, Hegseth has fired several top generals, admirals and other defense leaders.

Budget documents show the Pentagon plans to increase funding more than a hundredfold for an autonomous drone warfare program. The documents were released alongside other Pentagon budget materials in recent days.