TOKYO — A Japanese mayor who opposes moving a U.S. military base to his city in Okinawa has won a hard-fought re-election battle, dealing a potential blow to hopes in Washington and Tokyo that the long-delayed plan would move forward.

Nago city Mayor Susumu Inamine, who vowed to block construction of the base by denying permits for the project, declared victory Sunday night before 500 supporters at his campaign headquarters.

The U.S. and Japan agreed in 1996 to move the Marines Corps Futenma air station to Nago from a more congested part of Okinawa, but many Okinawans want the base off their island completely.

The plan got a boost last month when the governor of Okinawa gave the go-ahead for land reclamation to build the new base, whose runways would extend over water from the U.S. military's existing Camp Schwab. Opponents filed a lawsuit last week seeking to invalidate the governor's approval.

Inamine's victory will make it more difficult to move forward, analysts said.

"I don't think it'll be easy now for the U.S. base to be relocated, but I think there is a limit to what a local mayor can do," said Toshiyuki Shikata, a former Japanese military officer and professor of political science at Teikyo University in Tokyo.

The Futenma air station would be moved from Ginowan city to sparsely populated Henoko district in Nago, because of concerns about aircraft noise, accidents in civilian areas and base-related crimes such as rape. The proposed move is part of a broader plan to consolidate and reduce the U.S. military presence in Okinawa, currently home to about half of the U.S. troops in Japan.

Pre-election opinion polls by Okinawa media showed about 84 percent of Nago residents opposed moving the base to Henoko. Japan's ruling Liberal Democratic Party, which supports the move, wooed voters with promises of additional development funds for the city.

Inamine got 19,839 votes, versus pro-base challenger Bunshin Suematsu, who received 15,684.

"Despite all the efforts, the Liberal Democratic Party has lost," said Koichi Nakano, professor of political science at Sophia University in Tokyo. "I think it reflects how strongly people are opposed to a base relocation."

Before the vote, Hitoshi Morine, a spokesman for the Japanese Defense Ministry in Okinawa, said the government will seek bids soon for drilling surveys of the seafloor bedrock to begin designing the base.