YOKOSUKA, Japan (AP) — The new commander of the U.S. Navy's 7th Fleet assumed his post overseeing the world's largest forward-deployed naval force in a ceremony Saturday at a port just south of Tokyo.

Navy Vice Adm. John M. Bird was sworn in aboard the flagship USS Blue Ridge at Yokosuka port, the site of a U.S. naval base.

The 7th Fleet has 40 to 50 ships, 120 aircraft and about 20,000 sailors and Marines. Twenty-one of the ships are based in Japan and the Pacific island of Guam, while the others rotate out of ports in Hawaii and the U.S. West Coast.

Bird is now responsible for their deployment in an area covering 52 million square miles (135 million square kilometers) in the Pacific and Indian oceans that reaches the east coast of Africa.

Speaking at a ceremony attended by Japanese Maritime Self-Defense Forces chief Adm. Keiji Akahoshi, Bird promised to do his utmost to maintain peace and stability in the Asia-Pacific region, while strengthening the Japan-U.S. security alliance.

Outgoing Vice Adm. Doug Crowder will become deputy chief of naval operations in Washington, D.C., according to a Navy statement.

About 50,000 U.S. troops are based in Japan under a bilateral security pact.