[ythn]

Unless China and Russia do the same, there is little point in weakening yourself and your allies

[AnimalMuppet]

China, IIRC, only has 300 nukes. The US and Russia have ~2000 each. The US and Russia could go to 1000 each without feeling any need to wait for anyone else to disarm. (They'd probably want to do it in lockstep with each other, though...)