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.
Prime Minister 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.
Onaga told a news conference that he was ordering local defence ministry officials to halt the underwater survey work, which the prefecture fears is harming local coral reefs, a prefecture official said.
If those activities are not stopped within a week, Onaga may rescind approval for drilling operations given by his predecessor in December 2012, he said.
Delays to the plan to move the Futenma base to a less populous area of northern Okinawa could be a headache for Abe ahead of an April 26-May 3 visit to the United States, announced on Monday.
A summit with President Barack Obama is expected to highlight Washington's approval of Abe's more muscular security policy amid concerns about rising Chinese influence in the region.
Chief Cabinet Secretary Yoshihide Suga told a news conference the defence ministry was examining the documents from the governor but that the very fact he had taken this step was "extremely regrettable" since the work had previously been approved by the prefecture. That approval was given by Onaga's predecessor, whom he defeated in last year's election.
"At present we do not recognise any reason to halt the work," he said.
The United States 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.