Japan's central government on Friday formally asked Okinawa's governor to approve plans to build new US military facilities on the island, officials said, a vital step to ending a long-running dispute.

The move is the first in several years aimed at breaking the deadlock between Tokyo, which is bound to the US through a security treaty, and Okinawa, which resents bearing the burden of so many of the country's US bases.

Governor Hirokazu Nakaima received the request from the Japanese defence ministry asking that he give the go-ahead to plans to reclaim land off Henoko, central Okinawa, to build a runway for the US military, a spokesman said.

"Our governor will decide on whether to approve or not after looking into details of the request," the spokesman said.

Nakaima, who is authorised to approve all landfill projects on the island, is expected to make a decision in six to eight months, Japan's national broadcaster NHK reported.

But Nakaima already hinted he could reject the request, which is not backed by local people.

"I have been saying that (accepting the request) is virtually impossible and my thought has not been changed," the anti-base mayor told reporters in Okinawa.

The United States welcomed the move as a pivotal step toward "a sustainable US military presence with less impact on the Okinawan people," the Pentagon said in a statement.

"This is a key milestone that comes after many years of hard work between the United States and Japan," it said.

In 2006, Tokyo and Washington agreed to shift the controversial Futenma air base from a crowded city to the quiet area of Henoko and to cut the number of troops in Okinawa.

Locals have long complained of the noise from aircraft, the risk of accidents, and damage to the environment and want the base moved, but few in Okinawa would be happy to see it shifted within the island.

Prime Minister Shinzo Abe, who took office late December, met US President Barack Obama last month and confirmed the two countries would go ahead with the planned relocation of Futenma, despite local opposition.

"My basic policy is that we should not leave the Futenma (base) as it is for a long time," Abe told reporters in Tokyo after submitting the request. "I want to do my best to reduce people's burden."

Okinawa has been a longtime source of friction between the Pacific allies as the subtropical island is home to around half of the 47,000 US troops in Japan, who are stationed under a post-World War II security treaty.