TO Vietnam, a historic enemy of China, Beijing's plan is obvious: step-by-step control of the South China Sea. The problem is not everyone seems as concerned as Hanoi.
In late January, a new instance of Chinese territorial expansion was discovered. A Filipino fisherman reported being detained by Chinese sailors on a South China Sea reef claimed by the Philippines. A Chinese spokesman acknowledged that ''China's local fishing authorities have set up facilities at Meijijiao (Mischief Shoal, as it is called by the Philippines) to provide shelter for their fishing vessels.''
Hanoi officials were concerned immediately, since China had forcibly taken Vietnamese territory in the region before. ''We consider this a grave action,'' says a Vietnamese foreign ministry official. And he called the reaction of the US and Japan, the only two countries with the military might to oppose China, ''very weak.''
The South China Sea is a major waterway for ships working the world's most economically dynamic region. It's also the site for several companies exploring for underwater oil and gas.
THE best vantage point for monitoring the sea lanes and supplying drilling platforms is a chain of islands, reefs, and atolls called the Spratlys. Six nations claim all or part of the chain: China, Vietnam, Taiwan, Malaysia, the Philippines, and Brunei.
The country farthest from the Spratlys -- China -- has also been the most aggressive in asserting its claims.
Aside from taking control of the Philippine-claimed reef, in 1988 Chinese troops took a collection of reefs and islands held by Vietnam. Fourteen years earlier, during the endgame of the Vietnam war, China forcibly seized a group of islands called the Paracels, then controlled by South Vietnam.
Contravening international law, China claims virtually the entire Sea as its territorial waters.
Beijing's new pushiness in the Spratlys coincides with a defense and naval buildup in China and the political limbo created by the failing health of paramount leader Deng Xiaoping.
China recently approved a 15 percent increase in its defense budget and is scheduled to receive the first of four Russian kilo-class attack submarines.
The latest Chinese action has put the Association of Southeast Asian Nations, the regional alliance known as ASEAN, on the spot.
Malaysia, Brunei, and the Philippines, which make up the coalition along with Singapore, Indonesia, and Thailand, are among the six claimants.
In coming months, the issue is likely to strain the tenuous consensus within ASEAN.
Manila plans talks with China Sunday. As it presses its case, it is backed by Vietnam, which is due to join ASEAN this summer but lacks support from other members fearful of provoking Beijing. ASEAN meets in April to discuss security issues with China and late summer with the United States and other regional players.
Regional diplomats and analysts are questioning how quickly the dispute could erupt into a military clash as Chinese control over the Spratlys continues to spread.
''At present, it appears to be pretty safe if there is no oil discovery. Oil still remains a remote prospect,'' says Sheng Lijun, a Spratlys expert from China now based in Singapore. ''But if there is a major oil discovery, there could be trouble.''
''Will the Chinese strike before midyear when Vietnam is expected to become a member of ASEAN?'' asks Derek da Cunha, a regional defense expert at the Institute of Southeast Asian Studies in Singapore. ''Or will they not strike just yet, preferring to bide their time when an even more opportune moment arrives? Your guess is as good as mine.''
The Vietnamese Foreign Ministry official is less equivocal. ''One of the implications [of the latest incident] is that China would go ahead and press its claim and bring potential conflict into reality,'' he warns, adding that the US and Japan should be more vocal about Chinese aggression.
Betting that it can push its Spratly claims against less powerful nations without triggering a military conflict, China is concurrently urging a compromise of joint development among the claimants, an idea rejected by Vietnam.
''China can be flexible and could make some concessions on the historical waters,'' says Mr. Sheng, the Chinese foreign-policy researcher. ''But China won't give up its claim to the Spratly Islands.''
''On the issue of sovereignty in the Spratlys, compromise is out of the question,'' agrees a senior Western diplomat in Beijing.
In the meantime, some countries, such as Indonesia, which has pushed for a multilateral solution, would like to see the US, Japan, and other international powers intervene diplomatically to check China. ''With the help of the international community, ASEAN will gradually be able to resolve this problem with China over time,'' says a senior Indonesian diplomat in the region.
But other Asian analysts say the regional alliance is powerless and divided over the need to either take a stand or ease Chinese aggressiveness by forging closer economic ties. ''Currently, there is no other claimant or ASEAN country supporting the Philippines, except Vietnam,'' says a Southeast Asian policy analyst in Singapore. ''Both Singapore and Malaysia both want to get economic benefits from China, the US, and Japan. So they don't want to see a flare-up in the Spratlys.''