As the United States continues to formulate a comprehensive military plan against terrorists and the sponsors of terrorism, key Asian allies are contemplating how they will respond to requests for help. The countries appear set to take different approaches in their collective promise to support the United States.

In the week after the September 11 terrorist attacks in New York and Washington, most countries in Asia were quick to voice some form of support for U.S. action against terrorism.

But President Bush's blunt ultimatum Thursday for countries to declare their loyalty to U.S. plans for fighting terrorism has governments here facing crucial decisions.

Mr. Bush says if a country fails to show support, the United States could consider it a hostile nation. In light of this, analysts predict that most Asian nations with economies heavily tied to the United States will make some attempt to respond positively to Washington's proposals.

But Bangkok-based defense analyst Robert Carniol notes that there are five nations in Asia, Australia, Japan, the Philippines, South Korea and Thailand, that are not just encouraged, but obligated, to stand behind any U.S. military action. "Every one of them has a mutual defense treaty with the United States," he says. "The function of a mutual defense treaty is that if someone attacks us, you help. And if someone attacks you, we help. The help that can be provided varies in degree and type."

Of the five, Australia by far has been the most enthusiastic supporter of U.S. efforts. Last week, the Canberra government invoked a rarely-used clause in its defense treaty to authorize direct participation of Australian troops in an American military action.

Security expert John Hoadley in Auckland, New Zealand, says Australia is anxious to join in any military campaign that could ensure peace and stability in neighboring Indonesia, home to the world's largest Muslim population. "They have Indonesia on their northern border and they have refugees coming illegally on boats," he says. "So, all of this combined makes Australia a country very concerned about its security and it regards the United States as its most reliable ally."

South Korea and the Philippines have pledged their support by allowing their airports, seaports and military bases to be used in the hunt for terrorists.

Last week, the South Korean military also agreed to help the United States armed forces beef up anti-terrorism measures in Korea to protect the 37,000 U.S. troops stationed on the peninsula. The troops are there to protect South Korea from a possible invasion from communist North Korea.

In the Philippines, President Gloria Arroyo says while she is not ready to commit ground troops, she will give U.S. forces access to the former American bases at and near Subic Bay. The United States pulled out of the bases in the early 1990s after Manila showed reluctance to renew the leases.

But analysts say Japan's participation may be the most significant. Currently, Japan's post-World War II pacifist constitution prohibits the country from sending troops overseas and limits Japanese logistics support for U.S. military operations to a vague area near Japan. In 1991, Japan was severely criticized for declining to commit even a token force to the Gulf War. Instead it provided $13 billion in aid for American and allied operations against Iraq.

Prime Minister Junichiro Koizumi says Japan is determined not be isolated again. His government is expected to present new legislation in parliament next week that will enable the country to provide logistics support to the United States wherever it is needed.

Whether that means Japan would agree to transport lethal cargo like bombs and ammunition is still unclear, however. Mr. Carniol believes Japan is unlikely to offer specific details any time soon. "The Japanese way of approaching these things is to essentially not talk about stuff while they try to subtly build a public consensus," he says.

Thailand, too, is reacting cautiously and has not yet offered the United States specific assistance. Mr. Hoadley in Auckland says Bangkok is wary of upsetting Muslim communities, in the event U.S. attacks cause civilian casualties and suffering. "Not only are there Muslims in neighboring Malaysia, there is a couple of million Muslims living in southern Thailand," he says. "So, Thailand is perhaps trying to position itself as a more neutral country."

Analysts speculate that Thailand may also be hesitating because of its growing friendship with China and its overwhelming dependence on oil from the Middle East.