Japan's PM defiant on island claim No nation should ... underestimate the firmness of our resolve ... Japanese Prime Minister Shinzo Abe. THE Japanese Prime Minister, Shinzo Abe, has vowed he will not tolerate any challenge to control over contested islands, after China's growing incursions into the area. We simply cannot tolerate any challenge now and in the future. No nation should make any miscalculation or underestimate the firmness of our resolve," Mr Abe said at the Centre for Strategic and International Studies in Washington. No one should ever doubt the robustness of the Japan-US alliance. Speaking after talks at the White House with the US President, Barack Obama, Mr Abe also cautioned: "I have absolutely no intention to climb up the escalation ladder." He called for the two nations to work on common interests and called Japan's relations with China "among the most important" with any country. "The doors are always open on my side for the Chinese leaders," Mr Abe said. The Japanese leader insisted history and international law proved the islands - known as the Senkaku in Japanese and the Diaoyu in Chinese - "are Japan's sovereign territory." Japan has often charged that China only became interested in the East China Sea territory in recent times after learning it was potentially rich in oil and gas. China disputes the Japanese position and argues that it has controlled the islands since the 1368-1644 Ming Dynasty. Taiwan also claims the area. The Japanese chief cabinet secretary, Yoshihide Suga, said on Friday Tokyo had asked the Chinese government to explain why Chinese ships had placed several buoys near the islands. Mr Suga said that ships from China's State Oceanic Administration, which is similar to the coast guard, had placed the buoys last week in Chinese-controlled waters near the islands. Japanese media reported that the buoys might be used to track Japanese submarines in waters around the uninhabited islands, where Japanese and Chinese ships have chased each other in recent months. Agence France-Presse,