The first question for U.S. policymakers: What are America’s deterrence objectives for North Korea? In other words, what does it want North Korea not to do, and how can it be convinced not to do those things? Kim Jong Un must be made to understand that, under no uncertain terms, can he ever use his nuclear weapons; doing so would mean the end of North Korea. Whether the United States likes it or not, the country now poses a clear strategic threat, and it must be treated as such.

Deterrence is by no means a perfect solution, but for it to have a chance of success, the Trump administration must communicate directly with its North Korean counterparts to ensure they have a clear understanding of what actions would provoke a direct U.S. response. There are lots of ways to ensure North Korea gets the message, but none are as reliable or convincing as direct U.S. discussions with North Korean officials. These could take the form of military-to-military contacts, but whatever the choice, it will need to be well above the traditional channel U.S. diplomats have used in New York at the UN.

Even communicating through China, as the United States has done in the past, won’t be enough to ensure that Pyongyang feels the full impact of these messages. Those messages must make clear that the use of nuclear weapons, and any transfer of nuclear weapons or ICBMs or production capabilities to other states, is unacceptable. If America cannot prevent North Korea from possessing nuclear weapons, it has to make clear that any decision to use them would be the last one any North Korean leader would ever make. Senior officials in the Obama administration, where I worked on nuclear nonproliferation at the National Security Council, began to unpack these issues in anticipation that North Korea would continue to pursue an ICBM. It has now fallen to Trump to take that work and find a way to influence North Korea’s future actions.

As much as I would like North Korea to freeze and end its nuclear program, no combination of threats, engagement, negotiations, and sanctions, has produced that outcome. At best, any negotiations with the North must seek an agreement to avoid steps that could provoke a crisis, including no regular deployments of mobile missiles and an agreement to end or limit missile and nuclear weapon tests. In a perfect world, the United States could eventually start to negotiate an agreement where North Korea caps its nuclear program and stops producing materials that can be used to build nuclear weapons. But Washington does not know, and North Korea will not say, where all of its productions sites are. Nor will it allow inspectors access to verify they are shut down. Short of this, a ban is not viable and should not be a major focus of U.S. action.

The United States does not yet know what North Korea might demand in return for such constraints, but Washington and Seoul should consider offering their own steps that could reduce the risk of a military confrontation or escalation—something that’s in no one’s interest.