What is Trump's move is China puts out a statement like this(?):  "China opposes ANY US military initiative against North Korea unless and until North Korea except in response to direct military action by North Korea against the US."
Then what?  
I would think China has that card to play based on its logical interest in seeing NK unmolested for regime change purposes, and to prevent nuclear proliferation or conventional weapon deployment on the Korean Penninsula.  
What would the rest f the world respond with?  
Does this lead to the US being further isolated?
Is the world interested in seeing Donald Trump pushing "fire and fury" buttons at his personal whim?