Leaders of Japan and the Association of South-East Asian Nations were to start a three-day summit meeting in Tokyo Friday amid concerns about China's air defence zone, dpa reported. Japan is working with ASEAN on a response to China's air defence identification zone (ADIZ), declared in November, over a group of islets in the East China Sea, which are disputed with Tokyo. Japanese diplomats were working on a joint statement with their ASEAN counterparts, which would include a reference to ensuring freedom off light in international airspace, the Kyodo News agency reported.