TOKYO: Two decades ago, Japan's then-prime minister, Yasuhiro Nakasone, made headlines by calling his country an "unsinkable aircraft carrier" for US military forces in Asia.

Now his successor, Junichiro Koizumi, appears to be leaning toward an even bigger role for Japan as a strategic hub from which US forces can respond to threats in a wide "arc of instability" stretching from the Middle East to the Korean peninsula.

The proposed changes are part of Washington's plan to transform its military globally into a more flexible force to fight new threats such as terrorism and rogue states. They will likely be discussed when US Deputy Secretary of State Richard Armitage meets Japanese officials in Tokyo this week.

"The logic is clear: Japan is to commit further and further to the US global strategy," said Yoshihide Soeya, a Keio University professor of international relations. Tokyo, however, is treading carefully in meeting US demands for fear of angering local voters reluctant to host US troops and fueling charges that the government is exceeding the bounds of the security alliance and Japan's pacifist constitution.

Japan is host to some 47,000 US military personnel, with the largest presence, including about 20,000 Marines, on the southern island of Okinawa, one of Japan's poorest prefectures.

As part of the review of its global military distribution, the United States has already agreed with South Korea to withdraw 12,500 of its 37,000 troops from the country by 2008.

Few expect smooth sailing in talks with Tokyo, which coincide with Japan's own sweeping review of its defence posture, conclusions on which are due by the end of the year.

"This is a very gruelling task," Japanese Defence Minister Yoshinori Ohno said late last week. "We want to reach a conclusion quickly, but I'm not taking an optimistic view."

COMMAND FUNCTION: Among the ideas floated by the US side is to move the command function of the US Army 1st Corps, stationed at Fort Lewis in Washington state as a quick reaction force for the Pacific Rim, to the US Army Japan's Camp Zama near Tokyo.

Defence experts see the logic, but Tokyo is finding the proposal hard to swallow. "There is a certain concern that if the command function comes to Japan, transformation may extend the scope of the alliance beyond the Far East," said Shinji Yanai, a former Japanese ambassador to Washington.

He added that he personally did not share that concern. Other US proposals include relocating some Marines from Okinawa to Japan's mainland. That idea has been welcomed by many Okinawans, long resentful of what they see as their unfair share of the defence burden, but met with resistance by potential mainland host communities.

As one way to address the problem, Koizumi has suggested some US forces could be moved abroad. "It's a sort of bargaining," said a Japanese military expert. "We could accept 1st Corp's command function, but need to scrutinise the role of all facilities in Japan, and if we find some less important facilities, we may ask for their return."

OUTER LIMITS: Japan has been stretching the boundaries of both the US-Japan security treaty and its constitution for the past decade, most recently by sending troops to help rebuild Iraq.

US military forces in Japan are already deployed well beyond Asia, although the orders come from outside Japan. "The treaty talks about security in the Far East, but in reality, it has already gone beyond the traditional geographical definition," said Keio's Soeya.

"The current US moves would make it more explicit. "So the government has to find - it's an impossible task - but they have to find some logic to fill the gap between reality and Japan's post-war security parameters, and ultimately, the constitution," Soeya added.

Debate on revising Japan's constitution, which renounces the right to wage war but has been interpreted as allowing a standing military for defence, has already heated up. Both the ruling and main opposition parties are preparing proposals for changes. But with the politically sensitive process likely to take years, Japanese policy-makers are seeking other ways to justify the security shifts, perhaps by drafting new US-Japan guidelines on defence cooperation. "It's an ad hoc accommodation of the US reality," Inoguchi said. -Reuters