Defense Secretary James Mattis told reporters that hanging the military option over North Korea’s head is a way to “buy time” for diplomats to solve the crisis without war.

In August, National Security Advisor Gen. H.R. McMaster asked how the “classical deterrence theory” would “apply to a regime like the regime in North Korea.”

“A regime that engages in unspeakable brutality against its own people? A regime that poses a continuous threat to the its neighbors in the region and now may pose a threat, direct threat, to the United States with weapons of mass destruction? A regime that imprisons and murders anyone who seems to oppose that regime, including members of his own family, using sarin nerve gas in a public airport?” McMaster told ABC News. “…The most effective way of preserving peace is to be prepared for war.”

En route to Colorado Springs on Thursday, Mattis was asked if he agreed with McMaster that North Korea may not be deterrable.

“I think that is a question on a lot of people’s minds right now. Are they deterrable, are they not deterrable?” the Defense secretary replied. “And I think what that we have to do is try deal with the protection, defense of our country and our allies, and that’s where I stay focused right now.”

“I believe that we have to have good, strong defenses with our allies in order to buy time for the diplomats to resolve this situation,” he added. “I think we have to work with our allies to ensure that they know they have no military option, and allow the diplomats to solve the issue.”

Mattis would not reply when asked to interpret McMaster’s comments. “I’m not going to answer the question,” he said.

“I am involved in protecting the country, working with allies, buying time for diplomats to solve the basic problem. And that’s where I’m focused right now.”

“So long as they stop testing, stop developing, they don’t export the weapons, there would be opportunity for talks.”

Mattis emphasized that the effort is “being led right now diplomatically.”

“Everything we do is designed — the sanctions, the United Nations Security Council, two resolutions, unanimous resolutions, more economic sanctions, diplomatic persona non grata from a number of nations around the world — it’s all designed to bring diplomatic and economic pressure on North Korea to change its course,” he said.