Okinawans, voting for a new governor, are being asked to choose between the economic benefits of the bases and the burden of being host to some three-quarters of the US military facilities in Japan.
Keiko Itokazu -- who is backed by Japan's main opposition and would be the subtropical islands' first female governor -- wants to scale back the presence of US troops.
"I believe the only way for Okinawa to achieve economic independence is by getting the lands back from the US military bases and using them more productively for industry," she said Saturday to hundreds of supporters wearing pink armbands to back her campaign.
Polls show her running neck-and-neck with Hirokazu Nakaima, who is supported by Prime Minister Shinzo Abe's Liberal Democratic Party and seeks to replace the retiring fellow conservative Keiichi Inamine.
Nakaima has played down the base issue and focused on improving the economy of Okinawa, where unemployment runs twice the national average.
"Basically, negotiations with the United States will be through the central government," Nakaima told AFP after casting his vote.
Okinawa, which is strategically close to the Taiwan Strait, is home to more than half of the 40,000 US troops in Japan. Other than Afghanistan, the only other Asian country with a sizable permanent US military presence is South Korea, where the troops have encountered growing hostility.
Japan and the US agreed in May to pull out 8,000 of the 20,000 US troops from Okinawa to the US territory of Guam, in the most sweeping movement of troops in decades.
But the United States began installing Japan's first Patriot surface-to-air missiles in Okinawa after North Korea test fired seven missiles in July in Japan's direction.
Despite the fierce contest over the US military presence, Abe, a hardliner on North Korea, is seen as unlikely to agree to reduce troop numbers in the wake of the communist state's nuclear test last month.
Abe met Saturday in Hanoi with US President George W. Bush and agreed to step up cooperation on missile defense.
Shujiro Kato, a professor of political science at Toyo University, said sentiment was divided despite high-profile anti-US demonstrations.
"The election outcome in Okinawa is not easy to predict, because there is a significant silent voice that does not necessarily take the same position as
those with the big voice," he said.
One focal point of the race is Futenma air base in the crowded urban center of Ginowan. In 2004 a helicopter crashed in the campus of nearby Okinawa International University, fuelling the anger of residents.
Tokyo and Washington have agreed to dismantle the base and move Futenma's operations to another existing US base in Okinawa.
Itokazu is an outright opponent of the plan, while Nakaima has suggested he may reluctantly accept it to secure economic incentives from Tokyo.
Mizuki Nakamura, a 20-year-old student of the university, said it would be good to remove the base.
"But even if it's moved, if it's in Okinawa prefecture again, the risk of being targeted by North Korea would still be there," he said. "I have mixed feelings."
US troops are stationed under a security alliance reached after World War II, when defeated Japan was forced to renounce its right to a military.
Anti-US sentiment reached a crescendo in 1995 after the rape of a 12-year-old Japanese schoolgirl by three US servicemen.
"Because we host the US bases, we can get money," said Toshiyuki Kamiya, a 31-year-old company employee and father of three, referring to the economic subsidies from the government.
"But I also feel we need to think differently."

Copyright AFP (Agence France-Presse), 2006