The top-ranking U.S. military officer said Monday that North Korea's reported nuclear test is a primarily a diplomatic matter right now, not a military one.
"I think it's really important ... right now to emphasize the diplomatic path," Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, told CNN's "American Morning."
"Obviously we've got forces deployed to that part of the world, we have had for a significant period of time, we've got over 25,000 troops who are stationed in South Korea," he added. "We've got very close alliances there with Japan and South Korea as well. ... The countries who are involved in [the six-party talks], I think, are absolutely critical as we move forward to address this increasingly belligerent challenge from North Korea."
Mullen said the test did not come as a surprise to the United States.
"We weren't surprised because of recent statements by North Korean leadership that they intended to do this," he said.
"As you know, they also recently ... unsuccessfully launched potentially an intercontinental ballistic missile."
He said the reported test shows Pyongyang is becoming "increasingly belligerent."