Residents of a southern Japanese city voted Sunday in an unprecedented referendum on whether to accept the relocation of a U.S. naval air wing to an American base there.

The vote was not binding but has become a symbol of opposition to a major realignment of U.S. troops in Japan. The changes are part of the Pentagon's push to streamline its overseas bases and create a leaner, more flexible military.

More than 50 percent of Iwakuni's 85,000 eligible voters had cast ballots four hours before polling stations closed, said city official Fumitoshi Yoshiga. Officials had said votes would only be counted if turnout exceeded 50 percent.

Some Iwakuni residents, including the mayor, have opposed relocating the USS Kitty Hawk aircraft carrier from Tokyo to their city because of the risk of accidents and increased noise from nighttime fighter jet training.

Some 1,600 soldiers and 57 aircraft would be moved to the U.S. Marine Corps Air Station Iwakuni under the plan. Currently, 3,500 U.S. troops, most of them Marines, are stationed at Iwakuni, some 450 miles southwest of Tokyo.

"Just because the national government has decided something doesn't mean we must refrain from expressing our views," Mayor Katsusuke Ihara said, urging residents to vote.

Tokyo has made little headway in calming local opposition to the plan, but has been firm about wanting to complete the negotiations with the United States.

The repositioning of U.S. troops is also meant to ease tensions caused by the U.S. military presence, notably over soldiers accused of crimes.

About 50,000 U.S. military personnel are based in Japan, most on the southern island state of Okinawa, which was occupied by the United States at the end of World War II and returned to Japan in 1972.

Three U.S. servicemen were convicted of raping a 12-year-old girl there in 1995, sparking huge protests.

The case resulted in an agreement that the U.S. military would hand over American suspects in serious crimes to Japanese authorities for pre-indictment investigation.

Earlier this year, the head of U.S. forces in Japan apologized to Japanese defense officials over an American sailor's alleged killing of a Japanese woman in January. That attack took place near a U.S. Naval base in Yokosuka, about 30 miles southwest of Tokyo.

The total cost of the realignment for Japan could be more than $25 billion over 10 years, including a $8.5 billion plan to relocate a U.S. air base to another area on the island of Okinawa, the business newspaper Nihon Keizai reported, citing government estimates.