I wouldn't count on the US anymore, considering today's political climate. But in theory, EU+US could probably make a very compelling argument to China that if all three agree to play nice, nobody gets an advantage because of it, while everyone can benefit from a slower technological development leaving more time to figure out the societal problems.

Ultimately us random people on the internet can't say if China would want that or could be convinced with some other concessions unrelated to AI, but what we can say for sure is that, if China has the will to chill, the west has the negotiating power to match them.