China has very few 'strategic' capabilities. Their Navy is numerous but unable to project redoubtable force very far from it's shores.
They certainly recognize the futility of utilizing any nuclear assets against either japan, korea, taiwan or US possessions in the region.
It's biggest strength lies with it's army.. but without the means to move those forces off the mainland it is not a threat to us anywhere BUT the Korean penninsula. As long as the U.S. Navy remains in the Formosa straight, Taiwan will remain Chinas errant stepchild in revolt.
Short of deplyoing nuclear assets the chinese would be unstoppable should the decide to 'annex' their troublesome neighbors to the west. (N & S. Korea)
I suspect, considering the situation, should china declare that they intend to deal with NK, there won't be a single finger lifted in the west to dissuade them, no matter HOW loudly SK screams.