As the struggle to control disputed islands and valuable offshore resources intensified in the East and South China seas over the past few years, the United States has said repeatedly that it does not take sides in the disagreements among Asian countries over who has ownership rights.

Maintaining an impartial position helps the US to legitimise its "honest broker" role, and thus gain regional acceptance for moves to counterbalance growing Chinese power.

However, this has been easier for the US in the South China Sea than in the East China Sea because America's alliance bonds are looser and more ambiguous in the former, where only one of the four South-east Asian claimants, the Philippines, is a US ally.

In the East China Sea, America is tied by history and treaty to Japan's side in the current tensions between its ally and China.

Having the world's top three economies involved in this way makes the situation much more dangerous. It explains why the US is openly calling on Japan as well as China to handle the confrontation carefully and give primacy to maintaining peace and stability.

Noting Europe's slowdown and US economic difficulties, Mr Kurt Campbell, the US assistant secretary of state for East Asian and Pacific affairs, pointed out last Tuesday that East Asia was "the cockpit of the global economy, and the stakes (in the dispute over the Senkakus) could not be bigger".

The flare-up followed the Japanese government's decision last week to nationalise some of the Senkaku Islands in the East China Sea by buying them from private owners, despite Beijing's insistence that they belong to China.

In an orchestrated display of national resolution, China's top civilian and military leaders have all vowed to contest Japan's move to tighten administration of the Senkakus.

Even before Japan acted, senior Chinese military leaders visiting Washington expressed "China's strong concerns over issues related to China's vital and core interests", including US arms sales to Taiwan, territorial disputes over islands and maritime boundaries in the East and South China seas, and US close-range military reconnaissance activities directed at China.

Reporting on last month's visit, the official Xinhua news agency quoted General Cai Yingting, deputy chief of the Chinese armed forces general staff, as saying that China opposed the US stance that the Senkakus, which China calls the Diaoyu Islands, fall within the scope of the 1960 US-Japan Treaty of Mutual Cooperation and Security.

The treaty obliges Washington to help its ally if Japanese-administered islands come under foreign armed attack.

As if to underscore this commitment, Japanese forces and US marines are in the midst of a 37-day exercise to practise defence and recapture of vulnerable and lightly guarded islands in the Ryuku archipelago south of Japan.

The Senkakus are strategically located in this area between China, Taiwan and Japan. They are run by the Japanese authorities as part of the southernmost prefecture of Okinawa, where the US has a major military base. It serves as a hub for projecting American power and influence in East Asia.

Japan says it placed a sovereignty marker on the Senkakus in 1895 after surveys that found them unoccupied.

China contests this view, saying it discovered, named and used the islands going back to the early 15th century. It insists the Senkakus were administered by Taiwan (then ruled by imperial China) prior to 1895 when the islands were ceded to Japan in a treaty forced on China after it was defeated by Japan in a two-year war.

China (and Taiwan) say that they were promised at a 1943 meeting in Cairo with US and British leaders that when Japan was defeated, all the territories it had "stolen from the Chinese", including Formosa (Taiwan), would be restored to China.

Japan (and evidently the US) dispute the view that the Senkakus were part of Taiwan. They say that the 1951 peace treaty in San Francisco between victorious wartime allies and vanquished Japan placed the Senkakus and other southern Japanese islands under temporary US trusteeship.

This ended when a 1972 US-Japan treaty handed Okinawa and the surrounding islands back to Japanese control.

However, neither the People's Republic of China, which has ruled the mainland since 1949, nor the Republic of China on Taiwan, were invited to the San Francisco conference. Neither Beijing nor Taipei are parties to the treaty.

So far, China has talked tough but only carried small sticks in repeatedly asserting sovereignty over the Senkakus. Nothing it has done in the latest flare-up suggests that an invasion of the islands by Chinese regular armed forces is imminent.

China's Global Times, which often voices nationalist views and is controlled by the ruling Chinese Communist Party, noted last Tuesday that Japan had an advantage because it was in actual control of the Senkakus.

"Therefore, China should set a long-term goal, which is to change the current situation in terms of who controls the islands," the paper said.

China appears confident that as its economic and military power continues to grow, Japanese and US resolve to defend the Senkakus will diminish.

Meanwhile, the uninhabited islands remain a time bomb that could explode with devastating consequences for Asia if China, Japan or the US miscalculate.

The writer is a visiting senior research fellow at the Institute of Southeast Asian Studies.