The governor of Okinawa has lobbied lawmakers and officials in the United States to help reduce his prefecture's burden of hosting US military bases.
The southern prefecture of Okinawa hosts about 70 percent of US military facilities in Japan.
The US military and Japan's Self-Defense Forces are stepping up joint drills amid concerns over a possible contingency involving Taiwan.
Governor Tamaki Denny arrived in the US on Monday on a six-day visit. He met in Washington with officials of the US State Department and the Pentagon, as well as Congress members.
Tamaki reportedly described Okinawa's burden of hosting US military bases, and his opposition to the Japanese government's plan to relocate the US Marine Corps Futenma Air Station within the prefecture.
He also reportedly called for diplomatic efforts to ease tensions, saying Okinawa should never again become a battlefield.
Tamaki held a news conference at the National Press Club on Thursday but only one US media outlet participated among others.
Ahead of his return to Japan, Tamaki said he scored a significant achievement in directly conveying his opinions on the issues facing his prefecture.
He said he will study future directions after he returns to Okinawa.