ON THE face of things, North Korea was supposed to quiver at the presence of a powerful American aircraft-carrier, the USS George Washington, at the head of a fleet of American and South Korean warships off the south-east coast of the Korean peninsula this week. The vessels fired artillery shells and lobbed anti-submarine bombs into the wine-dark sea. This was no idle show of force, but an act of intimidation aimed at deterring North Korea, which South Korea and the United States blame for the sinking in March of a South Korean corvette, the Cheonan.

But more subtly, it was also a shot across China’s bows. China refuses to condemn North Korea over the Cheonan sinking, to the irritation of America and others, while describing the exercises as unwarranted warmongering. America and China have shown growing signs of friction over their competing security presence around the trade-clogged shores of Asia.

China’s reaction to the Cheonan is one element in what appears to be an attempt to turn the seas near it into a Chinese lake. South Korea had wanted to hold the joint war games in the Yellow Sea (see map), near where the Cheonan sank. But China said it opposed them, so the exercises were moved. It is the first time that China has objected to (perfectly legal) manoeuvres in the area. Chinese media reported that Chinese land forces had staged exercises of their own “near” the Yellow Sea.

Tensions are not confined to North-East Asia. On July 23rd they erupted publicly on the fringes of an Asian security forum in Hanoi, where Hillary Clinton, America’s secretary of state, said that respect for international law and established rules was key in the South China Sea. Vietnam, Indonesia, Malaysia, the Philippines, Taiwan and Brunei—all friendly with the United States—have maritime-boundary quarrels with China. An American role in enforcing the peace, Mrs Clinton asserted, was in her country’s “national interest”. The sea was “pivotal to regional stability”.

Two days later her Chinese counterpart, Yang Jiechi, struck back. He warned America off inflaming tensions by “internationalising” what Beijing insists are bilateral matters. Chinese editorials said South-East Asians should not be hoodwinked by imperialists. Last year America offered a pact of “strategic reassurance” with China, in which America would welcome China’s rise as a global power if it would reassure the world that it did not threaten others. The spat in Hanoi suggested that the pact has yet to materialise.

China ought to have seen Mrs Clinton’s comments coming. In March Chinese officials told Americans that they saw the South China Sea as part of China’s “core interests”, on a par with Taiwan and Tibet. In response Vietnam, which has chafed at China’s efforts to stop Western oil companies signing offshore oil exploration deals quietly led a lobbying attempt to get America to stand up for South-East Asia.

Some Americans urge a stronger response. Yet as Marcus Noland, a scholar of North Korea at the Peterson Institute for International Economics, argues, Mrs Clinton is constrained by the need for Chinese support on many issues. They range from exchange rates to Iran’s nuclear programme, and indeed to co-operation in the event of a North Korean meltdown.

Japan’s armed forces were present as observers during the Sea of Japan war games. Newspaper reports suggest the defence ministry will increase Japan’s submarine fleet for the first time since 1976, adding two submarines to counter both North Korea and increased Chinese naval activity in seas near Japan.

In South Korea, however, plenty have criticised President Lee Myung-bak for what they see as his hard-line approach to Kim Jong Il’s flailing regime. Conspiracy theories have swirled around the Cheonan investigation. One question was why Sweden, a part of the investigating team, did not sign the final report blaming North Korea. But the Swedish ambassador to South Korea, Lars Vargo, told The Economist that this was a procedural matter and his country believes North Korea was responsible.

In China the strength of the American response has sparked a debate over whether the country is pushing too far with its expanded list of “core interests”. On July 27th even the Global Times, a usually reliable critic of American behaviour, argued that China should avoid “arbitrarily expanding” the definition of its core interests. Sometimes even big powers, it said, can make territorial concessions without sacrifice. Outlook Weekly, part of the state news agency, quoted a military academic warning that to misuse the term “core interests” might undermine its deterrent value or even lead to armed conflict.

Just now, Chinese diplomats, for all the talk of China’s “peaceful rise”, have weakened their case by upping the ante. In the South China Sea, say Western diplomats, China has in effect declared as its territory not merely the contested Paracel and Spratly Islands and waters close to them, but a vast swathe of ocean stretching deep into South-East Asia. Neighbours wonder whether claims will one day be backed with force. “Does the expression of one’s legitimate concerns count as coercion?”, asked Mr Yang, the foreign minister. When it’s a colossus talking, China’s neighbours might understandably think so.

附註:或瞄或瞥還是蔡主席比較迷人!