The top nuclear envoys of South Korea and the United States urged North Korea on Wednesday to reengage in denuclearization dialogue.

South Korea’s Special Representative for Korean Peninsula Peace and Security Affairs Lee Do-hoon and his U.S. counterpart, Stephen Biegun, made the calls in respective speeches given at the Atlantic Council, a Washington-based think tank.

Lee, delivering his first public remarks in the U.S., urged North Korea to hold another summit with President Moon Jae-in ahead of U.S. President Donald Trump's visit to Seoul next week, saying now is a "golden opportunity" for North Korea. 

While affirming Seoul's enforcement of sanctions against North Korea, Lee stressed that sanctions are not magic bullets but are instead tools for bringing about solutions through negotiations.

Beigun said the U.S. and North Korea both understand the need for a "flexible approach" in denuclearization talks.

Stressing that the "door is wide open" to negotiations, Biegun said that the U.S. expects and hopes that in the not too distant future, North Korea will be reengaged in this process in a substantive way.

The two envoys both expressed hope that Chinese President Xi Jinping's trip to Pyongyang this week will play a constructive role in helping negotiations resume with the North.