The U.S. needs to counter China's claims to the South China Sea. Appeasement ALWAYS results in imperialists expanding territory, and eventually leads to war. As to Chinese cooperation in reining in North Korea, it will be patently obvious to them that a nuclear war on the Korean peninsula would, almost certainly, eventually involve China. It is in their own self-interest to stop the nut in Pyongyang before he starts a war.
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