North Korea remains an "extraordinary" threat to regional and global security, acting U.S. Secretary of Defense Patrick Shanahan said Saturday, calling on China and other countries to work closely for sanctions.

He, however, stressed his strong backing for diplomacy "to achieve the final, fully verified denuclearization of North Korea and uphold the international rule of law," in his keynote speech during the 18th Asia Security Summit, better known as the Shangri-La Dialogue, in Singapore. 

"North Korea remains an extraordinary threat and requires continued vigilance ... I think the first and foremost resolution is the enforcement of the U.N. Security resolution," Shanahan said.

He said that he has "full confidence in the ability to negotiate the fully denuclearized Korean Peninsula."

"On the policy side, my role ... is to be ready in the event diplomacy fails. My role in the Department of Defense is to enforce sanctions," he said, adding that the U.S. has "the appropriate readiness" in cooperation with South Korea and Japan.

Calling the Indo-Pacific "our priority theater," the Pentagon chief stressed the strong U.S. commitment to the region, including a huge investment in securing its stability.

Negotiations on North Korea's nuclear programs have been stalled since February when the second summit between U.S. President Donald Trump and North Korean leader Kim Jong-un ended without results.

In an apparent show of distrust, North Korea conducted weapons tests twice earlier this month, including two short-range missiles. (Yonhap)