What China wants to do is provoke Manila into throwing the first stone; the problem for Beijing is that, so long as the U.S. stands by their Filipino allies, they won't actually cross it. People forget that under the language of the 1951 MDT btwn Washington & Manila, the U.S. is obligated to assist if and only if the Philippines are attacked.
If Manila first the first shot, the U.S. is under no obligation to enter the fray, which explains to some degree what China is doing; they want Manila to act unilaterally and then "convince" Washington to stay out of things. FWIW, Washington should do the same thing it currently does w/both Japan and South Korea - extend its' nuclear arsenal over the Philippines, because that would be a clear sign of U.S. support for our long-time ally in the Southwest Pacific.