Authored by Stephen Herzog via WarOnTheRocks.com,

Given the vitriolic rhetoric between the United States and North Korea over the past year, few could have predicted that Supreme Leader Kim Jong Un would choose this time to implement a near-term moratorium on nuclear testing. Yet, here we are. On April 20, Kim announced precisely such a moratorium, along with closure of the Punggye-ri test site and a freeze on ballistic missile tests. Han Tae-song, the regime’s ambassador to the United Nations in Geneva, took the message a step further at the multilateral Conference on Disarmament, stating that the “DPRK will join international disarmament efforts for a total ban on nuclear tests.”

Experts are justifiably skeptical of the prospects for voluntary North Korean denuclearization. However, the regime’s rhetoric raises an opportunity for Kim and President Donald Trump to negotiate a formal end to the controversial testing program that has produced six underground nuclear explosions. One way to do this would be for North Korea to join the Comprehensive Nuclear-Test-Ban Treaty (CTBT).

The treaty has 183 state signatories — 166 have ratified — and bans “all nuclear explosions on Earth whether for military or for peaceful purposes.” Prior to returning to academia, I led U.S. Department of Energy technical delegations around the world to support the CTBT. Our team collaborated with foreign counterparts and the CTBT Organization (CTBTO) to enhance monitoring of nuclear explosions and other geophysical events, as well as prepare for future on-site inspections.

Based on my experience, North Korean accession to the CTBT deserves a hard, thoughtful look in both Washington and Pyongyang. Termination of nuclear tests on the Korean Peninsula is clearly in line with U.S. national security interests, and joining the treaty is a feasible concession for Kim to offer Trump. And the experts of the CTBTO are uniquely prepared to verify the permanent closure of Punggye-ri. Most importantly, the CTBT offers the best prospects for quickly rolling back elements of the North Korean nuclear weapons program.

With few up-front costs, Kim could signal his goodwill

Contrasting U.S. and North Korean definitions of denuclearization make nuclear disarmament appear unlikely in the next few years. North Korea recoiled at initial suggestions by U.S. officials that the regime should adopt the “Libya model” of complete, verifiable, irreversible dismantlement. Indeed, assessments by the CIA as well as the Pentagon have cast doubts on the possibility of denuclearization. Trump himself has now even tried to walk back expectations for the nuclear diplomacy.

But even if Kim isn’t prepared to give up his arsenal anytime soon, there are good reasons to believe he would be willing to accept the CTBT. Beyond North Korea’s statement in Geneva, Kim’s announcement of the moratorium strongly suggests he would be amenable to the treaty. He declared, “Under the proven condition of complete nuclear weapons, we no longer need any nuclear tests” and...