Relations between China and Japan have deteriorated since two Japan Coast Guard vessels collided with a Chinese fishing trawler in the waters off China's Diaoyu Islands in early September.

The illegal detention of the captain of the Chinese trawler by Japanese authorities and his prosecution under Japan's so-called domestic judicial procedures were unprecedented and enraged Chinese people. Japanese politicians even ignored China's "strong representations" against the incidents.

The way Japan handled the situation indicates the toughening of its stance toward China, which should be seen in the context of the United States' "return to Asia" strategy. The actions of the Japanese government, led by the Democratic Party of Japan, are apparently aimed at alienating China diplomatically.

The US' failure to get the desired political and military gains from the wars in Afghanistan and Iraq compelled it to withdraw some of its troops from Iraq and push for peace between Israelis and Palestinians. This, along with the US' declining economic and financial influence, prompted the Barack Obama administration to "return to Asia". The US believes its "return to Asia" strategy will not only help it to continue playing a leading role in the fast-developing continent and create conditions for its economic recovery, but also cope with the rise of China.

The US has strengthened its alliances with the Republic of Korea and Japan to make its "return to Asia" smooth and deal with traditional security issues in the region more effectively. It has worked out emergency military plans to handle possible crises on the Korean Peninsula and to gain the initiative in the Korean Peninsula denuclearization issue. The US has emphasized its "interests" in the South China Sea, too, to prevent its ally countries in the region from breaking away from its fold.

In Southeast and South Asia, it has taken concrete measures to boost political and security ties with member states of the Association of Southeast Asian Nations and India.

The US' unrestrained "return to Asia" and strengthening of its alliance with Japan - an important means of implementing its strategy - have influenced geopolitics in East Asia and caused negative effects on Sino-Japanese relations.

The changes in Tokyo's foreign policy, promoted by the ruling Democratic Party of Japan, is one of the main reasons behind the strained Sino-Japanese ties. Former Japanese prime minister Yukio Hatoyama's government resigned because of the controversy created by his move to "attach more importance to Asia" by changing his country's long-established US-centric diplomatic policy. Hatoyama's spat with American leaders over his efforts to make the US shift its air base from Okinawa added to the pressure on Hatoyama to resign.