Tensions between Asia's two most powerful economies ratcheted up further yesterday when Chinese ships again entered waters near the disputed island chain known in China as Diaoyu and in Japan as Senkaku.
The reported incursion by two Chinese surveillance ships and a fishing patrol boat prompted another official protest from Tokyo and an angry response from Japan's government spokesman Osamu Fujimura, who promised to "raise objections at the highest level".
Japan's government has so far resisted pressure from conservative politicians to send its Self-Defence Forces to the disputed region for fear of militarising the dispute. Japanese coast guard ships patrolling the region have been engaged in a game of cat and mouse with Chinese vessels for days.
News agencies in Taiwan and Hong Kong say Chinese activists from Hong Kong have threatened to sail on the five islets this week to challenge Japan's sovereignty. Japanese neo-nationalists are also promising another larger excursion to the area.
The row was triggered by Japan's nationalisation of three of the islets this month. The government of Prime Minister Yoshihiko Noda says it was blocking a more provocative attempt by Tokyo's right-wing governor, Shintaro Ishihara, to buy the islets from their private owner, but China says the nationalisation was "cooked up" by "right-wing elements".
Mr Noda has warned that anti-Japanese protests in China since the dispute began could harm his country's interests. Japan is China's biggest investor, and several large Japanese companies, including Sony, Panasonic and Toyota, have suspended some production and pulled staff back to Tokyo.
The world's second- and third-largest economies boast trade ties worth about $340bn a year. Tokyo is pinning its hopes for a diplomatic solution on Chikao Kawai, the Deputy Foreign Minister, who travels to China this week, but with both sides repeating the mantra that the islets are an "inherent" part of their territory, a solution is likely to be elusive. Mr Noda was expected to raise the dispute at the UN General Assembly yesterday.