The top U.S. nuclear envoy met with his South Korean counterpart Friday to discuss ways to resume the long-stalled negotiations aimed at ending North Korea's nuclear program, officials said.

The meeting between Sung Kim and Hwang Joon-kook, Seoul's special representative for peace and security affairs on the Korean Peninsula, came as Choe Ryong-hae, a special envoy of North Korean leader Kim Jong-un, told Russian officials during his recent trip to Moscow that Pyongyang is willing to resume the talks without preconditions.

"I hope we'll continue to work very closely together to achieve real progress in North Korea's nuclear issue and other important matters," Hwang said at the start of the meeting.

Kim said that it is "fate" that they can continue to work together on the North's nuclear issue, expressing hopes to have in-depth discussions.

Kim, a former U.S. ambassador to South Korea, arrived in Seoul a day earlier as part of his first trip to Northeast Asia as the top U.S. negotiator for the six-party talks on denuclearizing North Korea. He took office last month.

The six-party talks involving the two Koreas, the U.S., China, Russia and Japan have been stalled since late 2008, when Pyongyang walked away from the negotiating table.

Seoul and Washington have demanded the North first take concrete steps demonstrating its commitment to denuclearization.

China, a traditional ally of the North, has insisted that South Korea and the U.S. should lower the bar for the talks.

Pyongyang's recent release of all three Americans detained in North Korea has been widely seen as aimed at securing bilateral dialogue with Washington, analysts said. The U.S. has said that it offered no concessions for their release.

Kim's visit also comes amid reports that North Korean government officials and U.S. security experts are looking into a possible meeting in Singapore next month. 

South Korea's top nuclear envoy Hwang, meanwhile, returned to Seoul on Thursday from a four-day trip to Russia to discuss the North's nuclear issue.

Hwang told reporters in Moscow that Seoul is prepared to resume the six-party talks if the North shows strong signs that it will have "constructive dialogue" for denuclearization.

Kim, a career diplomat with expertise in the North Korean nuclear issue, became the top U.S. nuclear envoy after completing a three-year stint as ambassador to Seoul. Kim also doubles as deputy assistant secretary for Korea and Japan.

Kim's regional trip also includes three-day stops each in Japan and China. He will leave for Japan on Monday for a three-day visit.

Kim will then visit Beijing on Dec. 10 for talks with his Chinese counterpart Wu Dawei. (Yonhap)