“When we consider the presence of North Korea and the state of the wider region, it is clear that we must maintain the Japan-U.S. alliance as a deterrent force, and that we must ask Okinawa to bear some of that burden,” he said after the meeting with local leaders.

Image In his first visit to Okinawa since he became prime minister, Yukio Hatoyama, center, heard from residents of the island, home to a Marine air base. Credit... Kimimasa Mayama/European Pressphoto Agency

“It has become clear from our negotiations with the Americans that we cannot ask them to relocate the base to too far-flung a location,” he said.

Mr. Hatoyama still has not divulged the specifics of his plan. But it is widely expected that it will involve the small island of Tokunoshima, where since January, when word got out, residents have marshaled their resources for a fight.

Tokunoshima, a small, semitropical island located between Okinawa and Japan’s main islands and blanketed with fields of sugar cane, was mentioned as a possible site for training activities and up to 1,000 of Futenma’s 2,500 Marines, said Takeshi Tokuda, the island’s representative in the lower house of Parliament, who was briefed on the plan.

But enraged islanders vowed that the move would never happen. “If he comes, our old people and mothers with children will sit in the street to block his way,” Seiichi Yoshitama, 65, a coffee farmer, said of Mr. Hatoyama. “We’ll even use our fighting bulls to stop him.”

They have held a series of increasingly large anti-base rallies, the largest on April 18, when more than half of the island’s 26,000 residents gathered, organizers said.

The mood on Tokunoshima is now overwhelmingly against the plan. The main road along the coast is lined with hand-painted signs saying “No Base!” The mayors of the island’s three towns agreed on Saturday to meet with the prime minister, but only to express their opposition in person, they say.