The U.S. Defense Department says it is seeking to devise additional defensive measures against North Korea in the event diplomatic efforts fail.

Pentagon Press Secretary Geoff Morrell told reporters Tuesday that while the U.S. pursues diplomacy and economic sanctions against the North, it is also simultaneously working with South Korea, Japan and China on trying to devise additional defensive measures in the event that the North continues down its current path.

Asked about the possible U.S. reaction to the North’s recent nuclear test, Morrell said Washington’s focus was, is, and will likely continue to be on coming up with diplomatic and economic pressures that will persuade the North to abandon its nuclear ambitions.

Morrell said the U.S. will leave its options open in regards to the North, should Pyongyang continue to pursue nuclear weapons.