China is threatening war with US to improve their bargaining position wrt the 'Trade War' which is killing their economy
Also, every day that goes by, POTUS eliminates another backdoor that China had built into our military / industry / government … so everyday they wait, they become less potent against the US
The technical term for China threatening war with us is "saber rattling." If they wanted to go to war with us, they'd want it to be complete surprise.
All governments use the 4 instruments of national power (diplomatic, information, military, economic) together for ALL international endeavors.
Each instrument used to reinforce the position of the others.
Each instrument has a full spectrum of capabilities from supporting your closest ally to destroying your worst enemy