Defense Secretary James Mattis said Friday that should the United States be forced to engage in “a military solution” with North Korea, it would be “tragic on an unbelievable scale.”

Speaking during a Pentagon press conference, Mattis said there are “many different efforts underway” to curb North Korea’s aggressive missile program and tests. He noted there are both U.S. and international attempts to find a solution.

“We’re going to continue to work the issue,” he told reports. “If this goes to a military solution, it is going to be tragic on an unbelievable scale. So our effort is to work with the [United Nations], work with China, work with Japan, work with South Korea to try to find a way out of this situation.”

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Mattis’s comments come after North Korean this past weekend conducted a ballistic missile test.

The missile reached an altitude of roughly 1,300 miles and landed in the sea between Japan and the Korean Peninsula, more than 430 miles from its launch site.

The U.S. responded to the launch on May 13 by reaffirming its commitment to tightening sanctions against the North and urging the international community to do the same.

“We’re all aware of the provocative actions they’ve taken, and there have been cautions given them by nations around the world. They clearly aren’t listening, but there appears to be some impact by the Chinese working here,” he said.

“I spend as much time with the secretary of Treasury as I do with the secretary of State as we try to craft sustainable policy forward,” Mattis added.