In the present epoch the United States is NOT going to engage in nuclear disarmament. It will continue to attempt to limit or block nuclear disarmament by any non-major power (except, of course, Israel). This is because a central principle of U.S. foeeign policy is to presere its ability to attack any non-core nation. It has the military might to do that -- provided that that nation does not possess nuclear weapons. North Korea is safe because an attack onit would cause irreparble damage to South Korea nd Japan. It is certain that a small nation, any small nation, would not initiate nuclear war against the u.s. or any u.s. ally. Therefore North Korea's nuclear weapons, or the nuclear weapons I sincerely hope Iran can develop, will be no threat to peace but, rather, guarantees of peace. (Pakistan & India represent a seprate case and I have no opinion on the question there.)
Carrol