Japan expressed concern on Tuesday over China\'s expansion of maritime activities in waters around disputed islands in the East China Sea, saying such activities could cause a contingency. In its white paper on defense policy for 2013 approved by Prime Minister Shinzo Abe\'s Cabinet, the Defense Ministry said China has taken action described as coercive, which includes risky behavior in waters around the Japan-administered Senkaku Islands. \"China has attempted to change the status quo by force based on its own assertion, which is incompatible with the existing order of international law,\" the annual report said. The disputed islands are also claimed by China and Taiwan. Relations between the world\'s second and third-largest economies have sharply deteriorated since Tokyo\'s nationalization of three of the five major islands in September last year through purchase from a private Japanese owner. \"China\'s activities in Japanese sea and air include dangerous actions that could cause a contingency, and are extremely regrettable,\" the paper said. It particularly pointed out the radar targeting by a Chinese warship of a Japanese destroyer in January in the East China Sea. \"China should accept and stick to the international norms,\" it said. The defense white paper is the first to be published by Abe\'s government. The paper also expressed concern over North Korea\'s nuclear and ballistic missile development programs, warning that its missiles are potentially capable of reaching the US west coast, and even central states.