KADENA, Japan - Thousands of residents of Japan's southern island of Okinawa Saturday staged a protest against the presence of the US military on the eve of a major rally against a controversial airbase.

Some 2,500 people living in Kadena town, which already hosts a large US Air Force base that frequently provokes complaints over the noise of jet planes flying day and night, protested a government proposal the city accept another US military installation.

The demonstration came a day before Okinawans were to stage a major rally against a 2006 Japan-US military agreement ahead of US President Barack Obama's first visit to Tokyo.

Under the pact, Tokyo's then conservative government agreed with Washington that the US Marine Corps Futenma Air Base, which Okinawa has long demanded be moved out of a residential area, be relocated to the island's coastal Camp Schwab site.

New Prime Minister Yukio Hatoyama -- who swept to power in a landslide and has vowed a less subservient relationship with Washington -- said during the election campaign he would review the agreement and wanted the base moved off the island or even out of the country.

But under pressure from the United States, which has demanded Japan honour the pact, Foreign Minister Katsuya Okada proposed the Futenma operations be merged with the already existing air base in Kadena -- a suggestion that has angered Kadena residents.

"No matter what reasons or what explanations are given, I will never accept it," said Kadena mayor Tokujitsu Miyagi at the rally.

"Let's get rid of this proposal with our unshaken determination!"

More than 30,000 protesters were expected to gather Sunday against the 2006 agreement in a park near the Futenma Air Base in Ginowan city, organisers said.

The Futenma base, located in a densely populated urban area, has emerged as a flashpoint for local opponents who have been angered by aircraft noise, the risk of accidents and crimes committed by US service personnel.

"The Okinawan people are ready to shoulder the burdens of hosting the US military if the rest of Japan does the same," said Miyagi, whose town gives up about 83 percent of its land for the air base, according to town documents. "But what Okinawa has sacrificed has been just too much."

Washington and Tokyo have been close security allies in the post-war era, with the United States guaranteeing Japan's defence and providing nuclear deterrence during and after the Cold War.

Subtropical Okinawa, located about 1,600 kilometres (1,000 miles) south of Tokyo, is considered to be a strategic site near China, Taiwan and North Korea, hosting more than half of the 47,000 US troops stationed in the country.