"We continue to call on the DPRK (North Korea) to avoid any provocative behavior, become a responsible neighbor, and return to an authentic and credible diplomatic process towards our shared goal of denuclearization," Ambassador Sung Kim said.
Kim made the remarks during a security forum in Seoul hosted by Yonhap News Agency and the Asia-Pacific Research Center (APARC) of Stanford University.
"The process will not happen overnight. It will not be easy," Kim said. "But we will continue to press forward, in cooperation with our friends and allies in the region, to help build a Northeast Asia full of peace and prosperity."
North Korea has vowed to conduct its third nuclear test in response to the U.N. Security Council resolution tightening sanctions against it as punishment for its December rocket launch. The country previously detonated nuclear devices in 2006 and 2009.
Officials in Seoul have said North Korea appears to have completed all preparations and could detonate a nuclear device at any time.