U.S. Deputy Secretary of State Stephen Biegun said his talks with his South Korean counterpart Lee Do-hoon were "creative."
Speaking to reporters on Monday, he said they discussed constructive ways to continue advancing their diplomacy on the Korean Peninsula.
On North Korea, Biegun urged Pyeongyang to engage in talks as well.
"The U.S and ROK cannot do it by ourselves. We need DPRK engaged and we remain open to that discussion with them when they are prepared."
Biegun said the two sides also discussed the killing last week of a South Korean national by North Korean soldiers in the West Sea, saying it was something deeply disturbing to the Korean people and to the U.S.
Seoul's top nuclear envoy commented that of their recent talks, this round was the best, and that their cooperation will continue.
"I believe South Korea-U.S. cooperation is crucial now more than at any other time. Deputy Secretary Biegun and I have agreed to continue our talks through various channels."
Lee and Biegun also discussed issues related to denuclearization on the Korean Peninsula, though they did not release details.
This may have included the declaration of an official end to the Korean War, which to this day is suspended only by an armistice.
The idea was suggested last week by South Korean President Moon Jae-in in his speech to the virtual UN General Assembly.
Yoon Jung-min, Arirang News.