US Defense Secretary Jim Mattis said Friday that the Trump administration was working with its allies on a diplomatic solution to escalating tensions with North Korea.

Speaking with reporters in Mountain View, California, Mattis said his responsibility was to have military options available, but that the American effort was focused on diplomacy.

He pointed out that the UN Security Council unanimously voted last week to characterize North Korea’s statements as a “threat to the world’s community.”

“How often do you see France, China, Russia, the US voting unanimously on any issue?”

Mattis said the tragedy of war is well-known and “it doesn’t need another characterization beyond the fact that it would be catastrophic.”

North Korea on Thursday announced a detailed plan to launch a salvo of ballistic missiles toward the US Pacific territory of Guam, a major military hub and home to US bombers. If carried out, it would be the North’s most provocative missile launch to date.

Pyongyang has been louder in its complaints against a new and tough round of sanctions imposed by the United Nations, with strong US backing, and Washington’s use of Guam as a staging ground for its stealth bombers, which could be used to attack North Korea and are a particularly sore point with the ruling regime in Pyongyang.