U.S. Defense Secretary Jim Mattis said North Korea is acting in a reckless manner and must be stopped.

"This is a threat of both rhetoric and growing capability, and we will be working with the international community to address this, we are doing so right now," Mattis said in reply to a question about the potential threat to the United States from ballistic missiles.

"Right now it appears to be going in a very reckless manner in what its conduct is portraying for the future and that's got to be stopped," Mattis said.