Tokyo Gov. Shintaro Ishihara left for Washington on Sunday for a weeklong visit to the United States mainly for talks with senior government officials on the return of the U.S. Yokota air base in western Tokyo.

It is Ishihara’s second visit to the U.S. as governor. His first visit was in September 2001 when he was temporarily stranded following the September terrorist attacks in the U.S.

Yokota air base, one of three U.S. air bases in Japan, occupies around 700 hectares of land covering six municipalities in Tokyo. It accommodates the command headquarters of the U.S. forces in Japan.

Ishihara is campaigning to get the base back for civilian use to meet the rising demand for air travel in the nation’s capital.

The governor was in Washington when a hijacked passenger plane crashed into the Pentagon, just outside the U.S. capital, on Sept. 11 last year. He was forced to cancel the remaining items on his schedule for the visit.