China has refused to recognize North Korea is responsible for the Cheonan sinking.
The U.S. and South Korea are in an especially difficult spot here. Sinking a warship must have a strong response, but the response must be perfectly designed not to further ratchet up tensions. North and South Korea are one small mistake away from all-out war, and the costs of war are difficult to comprehend. South Korea’s capitol, Seoul, is within artillery distance of the demilitarized zone and would be almost immediately leveled if war breaks out.
China’s position makes this even more difficult. A unified response to North Korea would reduce the potential for increasing tensions. By refusing to recognize North Korea as responsible, though, China is preventing preventing that from happening.