TOKYO — Defense Secretary Pete Hegseth called Japan on Sunday an “indispensable partner” in deterring growing Chinese assertiveness in the region and announced upgrading the U.S. military command in Japan to a new “war-fighting headquarters.”

Hegseth, who is on his first Asia trip with Japan as his second stop, also stressed the need for both countries to do more to accelerate the strengthening of their military capability as the region faces China’s assertive military actions and…