A clash between Japan's central government and Okinawa island, host to the bulk of U.S. troops in Japan, deepened on Monday when the southern island's governor ordered a halt to underwater work at the site of a planned relocation of a U.S. Marine base. PM Shinzo Abe's government and Okinawa have been on a collision course since anti-base conservative Takeshi Onaga was elected governor last November and ruling party candidates were trounced in a December general election. The US(a) and Japan agreed in 1996 to close the Futenma Marines air base, located in a populous part of the island. But plans for a replacement stalled in the face of opposition from residents, many of whom associate the bases with noise, pollution and crime and resent bearing what they see as an unfair burden for the U.S.-Japan security alliance.

Okinawa, which was not returned to Japanese sovereignty until 27 years after Tokyo's defeat in World War Two, still hosts nearly 75 percent of the U.S. military presence in Japan, accounting for 18 percent of its land area.