North Korea's threats and recent actions represent a "real and clear danger" to the United States as well as its allies South Korea and Japan, US Defense Secretary Chuck Hagel said Wednesday.
"They have nuclear capacity now, they have missile delivery capacity now," Hagel said after giving a major strategy speech at the National Defense University, calling Pyongyang's "bellicose dangerous rhetoric" problematic.
"We take those threats seriously, we have to take those threats seriously," he added. "We are doing everything we can, working with the Chinese and others to defuse that situation on the peninsula.
"I hope the North will ratchet its very dangerous rhetoric down."
North Korea on Wednesday blocked access to the key Kaesong joint industrial zone with South Korea -- the only surviving example of inter-Korean cooperation and a crucial source of hard currency for Pyongyang.
The move represented a sharp escalation of a military crisis that has also seen the North threaten missile and nuclear strikes against the United States and its ally South Korea in response to UN sanctions and joint military drills.
Tensions have been soaring on the Korean peninsula since the North launched a long-range rocket in December and conducted its third nuclear test in February.
In a rare show of force in the region, Washington has deployed nuclear-capable US B-52s, B-2 stealth bombers and two US destroyers to South Korean air and sea space.
"We've been trying to work with the North Koreans to try to persuade them it's not in their interest, and certainly not in the Korean peninsula interest... to pursue nuclear weapons," Hagel said.
"There is a pathway that is responsible, for the North to get on the path to peace, working with their neighbors... but they've got to be a responsible member of the world community."