China's Xi says Japan's purchase of disputed isles a farce

Chinese leader-in-waiting Xi Jinping denounced Japan's decision to buy disputed islands as a farce and said Tokyo should "rein in its behavior" as China moved to snuff out anti-Japan protests.

Relations between Asia's two biggest economies have faltered badly, hitting their lowest point in decades on Tuesday when China marked the highly charged anniversary of the start of Japan's occupation of its giant neighbor in 1931.

Tension had run high on land and at sea, with four days of major protests in cities across China and Japanese and Chinese boats stalking each other in waters around a group of East China Sea islands, known by Japan as the Senkaku and by China as the Diaoyu.

"Japan should rein in its behavior and stop any words and acts that undermine China's sovereignty and territorial integrity," Xi said in a meeting with visiting U.S. Defense Secretary Leon Panetta, according to Xinhua news agency.

Xi, whose recent absence from public engagements sparked a series of rumors but was eventually pinned to a back injury, is expected to replace Hu Jintao as party chief at a Communist Party congress this year.

Xi has been known for using blunt language, and on this occasion he used it to become the first top Chinese leader to stake out a position on the islands since the uptick in tensions, promoting his own leadership credentials.

Like any new Chinese leader, Xi must try to establish his authority even while his predecessors retain considerable influence. The protests contained some criticism of Beijing as being too soft on its traditional Asian rival, creating pressures that could push China's incoming new leadership deeper into a diplomatic corner.

Chinese analysts and Western diplomats have said Xi is not the hardline, militarist nationalist of some portrayals. But activists campaigning for China to regain control of the islands said Xi would have to be more assertive than Hu in pressing Japan, or risk losing credibility.

Shi Yinhong, a professor in international relations at Renmin University in Beijing, said Xi's comments were "very normal" and would not encourage further protest.

"The Chinese government has discussed the anti-Japan protests but never encouraged them," Shi said. "It's very clear too that the Chinese government is about to open its 18th Party Congress. I think after September 18, the Chinese government will not encourage public opinion on these protests anymore."

Tokyo's nationalist governor, Shintaro Ishihara, floated a plan in April for metropolitan authorities to buy the islets, prompting Japan's government to buy them instead in a bid to defuse the crisis.

"If Japan yields to China on this problem ... China's hegemony in Asian waters would easily be established," Ishihara told the Tokyo Metropolitan Assembly.