The New York Times editors warn that reneging on the nuclear deal will undermine diplomacy with North Korea:
A serious negotiation with North Korea would include Mr. Trump pressing Mr. Kim to freeze nuclear and missile testing, halt the production of nuclear weapons fuel and the deployment of nuclear weapons and put an Iran-like verification system in place. But why would Mr. Kim agree to any of that if the Americans walk away from the Iran deal? Why would Mr. Kim, or any future adversary for that matter, assume Mr. Trump is negotiating in good faith?
Withdrawing from the nuclear deal would certainly send a message to North Korea that the U.S. can’t be trusted. The bigger problem with the Trump administration’s approach to North Korea is that the demands it is making of them have already told them that the U.S. is not interested in finding a compromise acceptable to both sides. “Complete, verifiable, and irreversible denuclearization” for the Trump administration doesn’t just mean the elimination of North Korea’s weapons, which is already unrealistic enough, but also extends to eliminating North Korea’s entire nuclear program. The administration is trying to reach a more ambitious goal with a nuclear-armed state than the JCPOA negotiators reached with a state that didn’t have nuclear weapons, and they are making the attempt with less leverage against an adversary that has even less incentive to agree to anything.
The Iran hawks both in the administration and outside it operate under the delusion that the U.S. can get an even more intrusive and restrictive agreement with North Korea than the one the P5+1 negotiated with Iran, but they can’t even get Iran to agree to make more concessions. One has to assume that they are setting such unrealistic goals for diplomacy with North Korea because they don’t want it to succeed, just as they have always wanted to tear down the nuclear deal with Iran.