Japan constantly makes trouble over the Diaoyu Islands issue and intends to strengthen its control over the islands. It initiated many provocative activities like naming the four subsidiary isles, promoting to purchase the Diaoyu Islands and holding fishing competition in the disputed waters.

Japan totally denies any substance to territorial disputes with China, but takes steps to strengthen the Diaoyu Islands as an "inalienable part" of itself. It takes a tough stance over the Diaoyu Islands dispute while acting very differently when confronted with territorial disputes with South Korea and Russia.

On June 28, seven politicians from South Korea's ruling party, the Saenuri Party, visited the Liancourt Rocks, known as Dokdo in Korean or Takeshima in Japanese. And a few days after, Russian Prime Minister Dmitry Medvedev officially visited the South Kuril Islands for the second time.

The Japanese government made protests against the visits to show their dissatisfaction. Russia now is enhancing its investment and infrastructure construction on the South Kuril Islands, and it has issued a plan to accelerate development of the islands during 2007 to 2015. Japan's protests seem to be weak.

Russia's actions and policies over the South Kuril Islands could be seen as a check on Japan's aggression on territorial disputes. South Korea also hopes China and Russia could be tough on the territorial disputes, so as to alleviate its pressure on the Liancourt Rocks issue.

Japan has different policies when handling the territorial disputes with the three countries. It offers token protests to show dissatisfaction to Russia and South Korea, but behaves decisively and toughly over the Diaoyu dispute. It not only prevents Chinese fishing boats from entering the surrounding waters, but also arrests and detains Chinese fishermen, and even takes tougher actions like ramming boats.

But Japan underestimates China's determination to safeguard its own sovereignty. After the boat collision incident in September 2010, China took unprecedented countermeasures when Japan extended the detention of the Chinese captain. It forced Japan to release the captain earlier than planned. This year, after Japanese provocations over the Diaoyu issue, the Chinese mainland and Taiwan are working together to defend the islands.

On July 4, members of the "World Chinese Alliance in Defense of the Diaoyu Islands" sailed into waters close to the islands. Taiwan's Coast Guard Administration sent five patrol boats to protect the vessel while in mainland, the Ministry of Foreign Affairs urged Japan not to endanger the security of those activists.

Cooperation is still limited across the Strait. The mainland government doesn't let the strong popular forces unite due to considerations over overall Sino-Japanese relations. If the government let them off the leash, popular sentiment defending the islands would be even stronger.

Objectively speaking, interaction and cooperation over the Diaoyu issue across the Straits will put much more heat on Japan. If Japan continues its steps in strengthening control over the islands, it will receive stronger reactions from both the mainland and Taiwan.

So far the Chinese government has been restrained over the Diaoyu issue. One prominent example is that the mainland doesn't allow activists or Diaoyu Islands defenders to go the islands, and nor does the Hong Kong government.

But if Japan continues seeking to smash the status quo despite China's restraint, it's very likely that China will take even tougher countermeasures.

The Noda government has misjudged the situation. It tries to nationalize the Diaoyu Islands and believes that there will be no strong reaction from China.

But from Chinese perspective, no matter whether the Tokyo metropolitan government or Japanese government purchases the Diaoyu Islands or nationalizes them by other means, it's still a step to consolidate the legality of Japan's control and jurisdiction over the Diaoyu Islands. China won't indulge such behavior, and will inevitably take strong countermeasures.

Japanese leaders should reflect on their aggressive territorial policies against China. They should learn from former Chinese leader Deng Xiaoping who had the strategic vision to develop bilateral relations by putting aside territorial disputes.

The author is deputy director of the Japan Study Center at China Foreign Affairs University. opinion@globaltimes.com.cn