A two-pronged U.S. strategy toward China over its contentious new air defense identification zone has baffled Japan, which relies heavily on Washington in dealing with Beijing's military expansion.

With regard to China's call for prior notification of foreign flights in the ADIZ, the United States showed signs Friday of making a concession on the operation of commercial aircraft but kept playing hardball militarily.

The U.S. State Department surprised Japanese officials as it effectively advised U.S. airlines to meet the Chinese call to submit flight plans before their aircraft enter the air defense zone set up over the East China Sea.