Whenever China wants to identify the issues considered important enough to go to war over, it uses the term “core interests.” The phrase was once restricted to Taiwan, the island nation that China has threatened to forcibly unify with the mainland. About five years ago, Chinese leaders expanded the term to include Tibet and Xinjiang, two provinces with indigenous autonomy movements that Beijing has worked feverishly to control.

Since then, Chinese officials have spoken more broadly about economic growth, territorial integrity and preserving the Communist system. But recently they narrowed their sights again, extending the term explicitly to the East China Sea, where Beijing and Tokyo are dangerously squabbling over some uninhabited islands. Top Chinese military officials first delivered the message to Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, when he visited Beijing last month. The next day, the Foreign Ministry spokeswoman, Hua Chunying, told reporters that “the Diaoyu Islands are about sovereignty and territorial integrity. Of course it’s China’s core interest.”

This wording, with its threatening implications, is raising new tensions in a region already on edge over North Korea and several other maritime disputes, and it will make it harder to peacefully resolve the dispute over the islands, called Diaoyu in China, and Senkaku in Japan.

While Japan has held the islands for more than a century, China also claims title and has sent armed ships and planes from civilian maritime agencies to assert a presence around them. The waters adjacent to the islands are believed to hold oil and gas deposits.