NAGO, Okinawa Pref. -- This sleepy northern Okinawa city is gearing up to hold the first plebiscite in the nation on allowing the introduction of a U.S. military base, and the campaigns for and against the planned U.S. Marine Corps offshore heliport are getting heated.

The facility will be adjacent to the U.S. Marines Corps Camp Schwab, situated in the Henoko district, and would take over key functions of the Futenma Air Station in Ginowan. The Futenma base is to be relocated from its central Okinawa Island location in accordance with an agreement made last December by the Japan-U.S. special action committee.

The outcome of the Dec. 21 plebiscite could have a major impact on Prime Minister Ryutaro Hashimoto's ability to live up to his obligations under the Japan-U.S. security treaty, because he has repeatedly promised not to build the facility without a local consensus. Taking advantage of the 25th anniversary of Okinawa's 1972 return from the U.S., Hashimoto recently attended a ceremony in the prefecture to unveil an Okinawa economic promotion plan for the 21st century.

He then sought local support for the sea-based heliport, calling it necessary and "the most realistic option" to effect Futenma's return and to maintain the Japan-U.S. security arrangement. Although Hashimoto scoffed at suggestions that he is using the economic package to drum up local support for the heliport, critics claim he has left Okinawa with the harshest of options: future prosperity but with a U.S. base attached, or a moral victory for locals who will pay the price by remaining in a hopelessly undeveloped economy.

Flags, banners and billboards can be seen all over town, and campaign trucks from both sides of the debate cruise the streets blaring their slogans and collecting signatures. "We must make the most of this once-in-a-100-year opportunity to seize the promotion measures for the city's major economic development," said Susumu Asato, a representative of a municipal assembly members' conference promoting the heliport.

More than 500 people, many from the local chamber of commerce, took to the streets in a rally organized by the Citizens Group for the Vitalization of Nago. The group, which is for the heliport, has snowballed into a conglomeration of 37 conservative bodies, which include fishermen, contractors, tour agencies and owners of land used by the military.

At a local civic center, an opposing group called the Conference against the Heliport held a rally attended by some 3,000 people. The organization is made up of 22 groups, including labor unions, grassroots organizations and some ruling parties in the prefectural government.

Tensions have been rising sharply since early October, when the Nago assembly decided to hold the plebiscite. When it was first proposed in September by opponents to the heliport, with signatures from some 17,000 voters (46 percent of the electorate), the plebiscite offered only two simple choices -- for or against.

Mayor Tetsuya Higa, however, in an effort to provide a wider range of choices, revised the proposal soon afterward by adding two conditions: "Yes, because we can expect to receive subsequent positive economic effects and environmental safety measures," and "No, because we cannot expect such promises to come through." It is thought the mayor's move gave heliport proponents a greater advantage.

At that camp's rally, Asato said the central government's plan to boost the amount of base-linked grants to 2 billion yen or 3 billion yen from the current 70 million yen would significantly contribute to development of Nago's culture, education and social welfare. Nago's general account budget stands at about 24 billion yen, but several hundred billion yen will reportedly be needed if either of the two proposed methods of construction of the heliport is chosen. One calls for a platform supported by stilts sunk into the sea bottom inside a coral reef. The other is a floating pontoon platform moored outside the reef.

"The subsequent economic impact would amount to trillions of yen," said Kenjiro Nishida, a former chairman of the prefectural chapter of the Liberal Democratic Party. Nishida cited offers by the central government to build such facilities as a national technical college and an NTT telephone directory information center, as well as improve urban areas and the transportation infrastructure.

"This may be the last chance for reviving the northern part of Okinawa Island, which has been lagging behind economically compared with the middle and southern parts, while at the same time being deprived of its water and workforce," Nishida said.

More than 2,000 people, or about 10 percent of Nago's potential workforce, are jobless, and a large segment of them are under 30. Flanked by mountains and forests, Nago's 54,600 people depend largely on agriculture, food processing, poultry and hog farming to earn a living.

Regardless of whether the compensatory financial aide from the central government can remedy Nago's moribund economy and the other vast, rugged areas of northern Okinawa, those opposed to the heliport care less about money. They feel an additional base will disturb the marine and mountain environments and their own peace of mind.

Opposition groups say almost 70 percent of the U.S. bases in Okinawa are already concentrated in Yambaru, Okinawa's northern district. They call the area the rubbish heap of bases. "Only two years after the incident (the rape of a local schoolgirl by three U.S. servicemen), the government is trying to build a new base in the very area where it occurred," said Yasuhiro Miyagi, 37, a representative of the conference against the heliport. "Some insist on the need to protect the urban area, but we want to protect our lives."

Other participants at the rally accused the central government of splitting the opposition movement with the economic carrot, and of neglecting to conduct an adequate feasibility study for the heliport.

Earlier explanatory meetings held by the Defense Agency-led Futenma special task force with all 38,000 local eligible voters apparently failed to allay the opposition. "The government's feasibility study proved how negligent it is toward nature and science," said Tomoyasu Kawai, director of Japan Scientists' Association, who organized a study jointly with other private research institutes of the local marine environment.

Coral reefs off the Henoko district that were once threatened are steadily recovering, and seaweed is growing thick enough to feed such protected sea mammals as dugongs, he said. "As a scientist, I felt a sense of anger toward the government attitude of attaching greater importance to military bases."

With opponents unable to boast a promising plan for the future without the bases, however, the Dec. 21 plebiscite is expected to be a close race. Nonetheless, Miyagi urged citizens to review Nago's financial management before looking for national economic support, pointing out that the 5 trillion yen the central government previously allocated to Okinawa for public enterprises since its return in 1972 did not help the prefecture stand on its own feet.