Prominent US liberal activists on Wednesday pledged solidarity with Okinawa residents opposed to a US military base, despite efforts by Japan and the United States to finalize a relocation plan.

More than 100 scholars and activists including the filmmakers Oliver Stone and Michael Moore signed a joint statement opposed to construction of a US Marine base in Nago, a quiet town on the east coast of the subtropical Japanese island, to replace the aging and unpopular Futenma Air Station.

"Not unlike the 20th century US civil rights struggle, Okinawans have non-violently pressed for the end to their military colonization," the statement said.

"We support the people of Okinawa in their non-violent struggle for peace, dignity, human rights and protection of the environment," it said.

Other signatories included two leading US scholars of modern Japan, the Pulitzer Prize winners Herbert Bix and John W. Dower, along with linguist and left-wing activist Noam Chomsky and Daniel Ellsberg, the former military analyst who leaked the secret Pentagon Papers on the Vietnam War.

Okinawa, which was administered by the United States until 1972, hosts the bulk of the 47,000 US troops in Japan. Futenma has been a particular source of grievance due to its proximity to crowded urban areas.

US officials insist that the plan to move the base to more remote Nago is meant to respond to residents' concerns while ensuring the defense of Japan, which has been officially pacifist since World War II. Okinawa is strategically close to waters that have seen rising tensions between Japan and China.

Japan and the United States agreed on the relocation plan in 1996 but opponents have campaigned to remove the base altogether, accusing US troops of noise and crime.

Japanese Prime Minister Shinzo Abe, a conservative who supports stronger defense, appeared to achieve a breakthrough in December when Okinawa's governor accepted the relocation plan after promises of at least 300 billion yen ($2.9 billion) in aid every year until 2021.

But the plan hit a fresh setback earlier this month when the town of Nago re-elected a mayor opposed to the base.