the US won't take abandonment of No First Use by China seriously. By the time China can build up a matching number of nuclear warheads, it would most probably have built up sufficient conventiion naval strength to stop the US navy to get close to Taiwan and there would make an abandonment of the No First Use unnecessary!

But China needs to build up matching number of nuclear warheads, and missiles, so as not to be held hostage to possible nuclear blackmails by the 2 nuclear superpowers.