Pompeo did not specify whether arresting the North’s nuclear development would come by way of sanctions, negotiations, or more forceful means. But he did highlight North Korea’s nuclear and missile tests as obstacles to achieving the goal. “Their testing capacity has improved and the frequency that they have tests which are materially successful has also improved,” he said.

Pompeo also added two notable caveats to Trump’s “It won’t happen!” vow. The first was that the president is intent on preventing North Korea from developing an arsenal of long-range nuclear weapons. This is different from a posture that insists on preventing the successful test-firing of a single weapon, which is the one Trump seemed to embrace in his tweet. “The logical next step would be [for North Korean leader Kim Jong Un] to develop an arsenal of weapons. Not one, not a showpiece … but rather the capacity to deliver [nuclear weapons] from multiple firings of these missiles simultaneously. And that increases the risk to America, and that’s the very mission set that President Trump has directed the government to figure out a way to make sure it never occurs.”

The second caveat was that the administration is determined to deny North Korea reliable long-range nuclear weapons. “Can they reliably deliver the pain which Kim Jong Un wants to be able to deliver against the United States of America?” Pompeo asked. “It’s one thing to be able to say ‘Yes it’s possible you could if everything went right’—‘if the missile flew in the right direction and we got lucky, we could do it’—as opposed to certainty.”

“This is the core of deterrence theory: You have to be certain that what you aim to deliver will actually be successful. At the very least you need to make sure your adversary believes that it is certain,” Pompeo continued. “That’s what Kim Jong Un is driving for. He is trying to put in our mind the reality that he can deliver that pain to the United States of America. And our mission is to make the day that he can do that as far off as possible.”

Pompeo said that while the CIA assesses Kim Jong Un to be a “rational actor,” the agency is concerned that Kim “may not be getting really good, accurate information” about how serious the United States is about countering North Korea’s nuclear program. “It is not a healthy thing to be a senior leader and bring bad news to Kim Jong Un,” he joked. “Tell someone you’re going to do that and try to get life insurance. So we’re taking the real-world actions that we think will make unmistakeable to Kim Jong Un that we are intent on denuclearization. We are counting on the fact that he’ll see it. We’re confident that he will.”

And even if Kim is a rational leader who could be deterred from using his nukes, failing to end North Korea’s weapons program could result in a nuclear-arms race in the region, with the North sharing its nuclear technology with other countries or groups, and Kim Jong Un using his newfound clout for “coercive” purposes. “We do believe that Kim Jong Un, given these tool sets, would use them for things besides simply regime protection,” Pompeo explained. “And that is to put pressure on what is his ultimate goal, which is reunification of the peninsula under his authority.”