TOKYO: The United States is ready to face "a variety of different possibilities" in talks with Japan on where to relocate a contentious US military base, its top diplomat for Asia was quoted as saying Thursday.

The base issue has soured ties between Washington and Tokyo since Prime Minister Yukio Hatoyama's centre-left government took power in September, promising a less subservient stance toward the United States.

The row centres on the US Marine Corps Futenma Air Station on southern Okinawa island which many locals want closed, citing aircraft noise, pollution, the risk of accidents and past crimes committed by American troops.

Japan's new government has launched a review of a 2006 agreement to move the base from a crowded urban area to a quieter coastal part of the island, saying it may have to be moved off Okinawa instead or even outside Japan.

The top US diplomat, in an interview with a Japanese newspaper, said Washington still wants Tokyo to honour the original plan to move the base to Okinawa's coastal Henoko, but signalled it is open to negotiations.

"Again, our preference is for the current plan to go forward, but we are prepared to face a variety of different possibilities going forward," said Kurt Campbell, US assistant secretary of state for East Asian and Pacific Affairs.

"I am not going to get into the specifics, but we also have studied many different potential solutions very closely, not over a period of months, but years," he was quoted as saying by the Sankei Shimbun daily.

"So we will be able to provide Japanese counterparts with some of the challenges and weaknesses of other approaches," he added, according to the original English comments provided to AFP by the newspaper.

The relocation agreed by previous conservative governments on both sides in 2006 is part of a wider plan to realign the 47,000-strong US troop presence in Japan, where American forces have been based since the end of World War II.

Hatoyama, whose ruling coalition includes the strongly pacifist Social Democrats, has said he will decide by May whether to stick with the pact or move the base to another site, either on or off the island.