China's Coercive Play - NYTimes.com China's decision to impose a new air defense zone over a wide swath of the East China Sea is at odds with its claim to want a peaceful resolution to territorial disputes over a group of islands there. The announcement is a highly provocative move that has increased tensions and could make direct conflict with Japan more likely. On Saturday, China declared the zone around the islands, called Senkaku in Japan and Diaoyu in China, and asserted the right to require aircraft entering the space to identify themselves and possibly to take military action against those that do not. The uninhabited islands, some no more than piles of rocks, are administered by Japan but claimed by China and Taiwan. For more than a year, China and Japan, the world's second- and third-largest economies, have been increasingly confrontational over the issue. Japan's hypernationalist government led by Prime Minister Shinzo Abe has most often been the provocateur, but China has contributed to the instability by deploying Chinese coast guard ships and aircraft to the area to challenge Japan's claims. The air defense zone goes even further in contesting Japan's control by aggressively asserting China's reach in the region. It significantly complicates efforts by the United States to develop a relationship with China under President Xi Jinping. Asian airlines quickly fell in line and said they would inform China of their flight plans before entering the disputed airspace. But the unilateral power grab rightly angered Tokyo and Washington. On Saturday, Defense Secretary Chuck Hagel, as part of a rapid American response, made it clear that the announcement "will not in any way change how the United States conducts military operations in the region" and reaffirmed America's treaty obligation to aid Japan if it were attacked. On Monday, Mr. Abe vowed to defend his nation's airspace. Given China's unilateral decision, with its threat of possible military action, the United States needed to stand up for its ally Japan, for the principle of freedom of navigation of the seas and skies, and for other Asian nations that also have territorial disputes with China in the East China Sea and the South China Sea. Although America recognizes Japan as the administrator of the islands, it takes no position on claims to the islands in general and has urged all claimants to peacefully resolve their disputes. But Mr. Abe has pursued a disturbingly nationalistic foreign policy dominated by overheated words and an aggressive posture toward China that can be dangerous, for Japan and the United States. The Obama administration must find a way to defend Japan's interest without emboldening the Abe government to take foolish risks that would increase tensions with China. Along with its predecessors, the administration has not always been clear or consistent in its messages and that needs to change. But it is China's behavior that is most disturbing right now, especially since officials have left open the possibility of more air defense zones in the future. The United States has urged China to exercise caution and restraint and should be increasingly active in helping the two nations find a path away from confrontation. It is unclear if China really intends to respond militarily to Japanese or other planes flying through the zone, but the chance of miscalculation or error grows as the dispute escalates. China's action casts a black cloud over Vice President Joseph Biden Jr."s trip to China next month. It also raises new questions about what President Xi meant when he said earlier this year that he hoped to work out a "new type of great-power relationship" with President Obama.