Singapore ? U.S. Defense Secretary Robert Gates challenged China to deal realistically with the short-term question of how to respond to an antagonistic North Korea and the longer-term issue of whether Beijing’s expanding military can establish more durable ties with the U.S.

Asian nations cannot stand by in the face of North Korea’s alleged sinking of a South Korean warship, Gates said during an international security summit Saturday that was dominated by questions about the North.

The latest crisis with North Korea points out the limited options to deter further attacks or dismantle its nascent nuclear weapons program. The United States and China were part of a diplomatic effort to buy out the North’s nuclear program that fell apart two years ago.