An armed conflict between the U.S. and Pyongyang would be a catastrophic event, U.S. Secretary of Defense James Mattis told reporters on Thursday evening.

Speaking to reporters in Mountain View, California, Mattis said that U.S. efforts on North Korea were currently focused on diplomacy, while stressing that his “mission” was to make sure Washington “is to have military options should they be needed.”

“The tragedy of war is well enough known,” Mattis said, responding to a question about the human toll of a nuclear confrontation between the DPRK and the U.S. “It doesn’t need another characterization beyond the fact that it