China’s top nuclear envoy, Wu Dawei, has departed for Japan after wrapping up a three-day stay in Seoul.

Earlier on Friday, Wu met with First Vice Foreign Minister Shin Kak-soo and senior presidential secretary for foreign affairs and security, Kim Sung-hwan, and discussed the resumption of the six-way nuclear talks.

During the meeting, Wu talked about his trip to North Korea last week and asked for Seoul’s cooperation to get the stalled nuclear negotiations back on track.

In particular, Wu called for Seoul’s cooperation toward China’s three-step proposal to reopening the six-nation nuclear talks, citing that Pyongyang had agreed to support such a proposal.

China’s proposal seeks to have Pyongyang and Washington first hold bilateral talks before all six parties hold an informal preparatory meeting followed by an official session.

In response to Wu’s remarks, South Korean officials reiterated that in order for the six-nation talks to reopen, North Korea must first assume responsibility for the sinking of the “Cheonan” naval ship and make substantial moves toward denuclearization.