SEOUL, Feb. 19 (Yonhap) -- The international community has failed to reduce the threat posed by North Korea over the past 20 years, and the United States could be vulnerable to terrorist attacks using the North's nuclear devices, a former U.S. assistant Secretary of State said Tuesday.

"The policy we have pursued over the last 20 years -- engagement, containment, whatever -- has failed to reduce the threat posed by North Korea to the security of the region," Robert Gallucci said in a keynote speech during a security forum held in downtown Seoul.