It’s really an agreement to work towards disarmament, not to just unilaterally disarm regardless of what everyone else is doing.

Article VI: Each party “undertakes to pursue negotiations in good faith on effective measures relating to cessation of the nuclear arms race at an early date and to nuclear disarmament, and on a Treaty on general and complete disarmament under strict and effective international control”.

I can’t see how for example Russia could be disarmed under strict and effective international control in the current climate.

We’re not increasing the number of our warheads in service, just replacing old ones with a new design.