Who is pushing the problem on?
This situation is this, from the NK perspective, they are still technically at war with the U.S. and they've watched the U.S. deliver regime change around the globe and are, rightly, worried that eventually the U.S. will turn it's eye back on them. The only way to put a stop to that is to present a credible threat for extremely large losses should the U.S. invade, so much so that it deters them from invading in the first place.
The best way to achieve that is through having nuclear weapons, so they won't give them up. Any other assurances or treaties aren't worth the paper they are printed on with the U.S., as they will just pull out or change them as and when it suits them, or when a new government is voted in.
