James Mattis in The Associated Press

On War & Peace: North Korea must be stopped, but by diplomatic means

"This is a threat of both rhetoric and growing capability," Mattis said, alluding to the North's recent progress in building nuclear bombs and developing an intercontinental ballistic missile to deliver such weapons to U.S. soil. The Trump administration has been conducting a broad policy review of North Korea that includes military options, but Mattis stressed other approaches. "We are working diplomatically, including with those that we might be able to enlist in this effort to get North Korea under control," he said. "But right now it appears to be going in a very reckless manner. That's got to be stopped."