LONDON (Yonhap News) ― North Korea’s chief negotiator to the stalled six-party talks and U.S. civilian experts on the Korean Peninsula held informal talks in London on the current impasse surrounding the communist country’s nuclear ambitions, sources said Wednesday.

The meeting comes as Pyongyang has repeatedly called for unconditional talks to resolve the nuclear standoff, although Washington has made clear that the North must first show its firm commitment to past denuclearization pledges before meaningful negotiations can resume.

Sources said Ri Yong-ho, the North’s senior delegate to the six-party negotiations, met Stephen Bosworth, former top U.S. negotiator on North Korea’s nuclear program, and Joseph Detrani, former mission manager at the Director of National Intelligence.

They did not give details on what was discussed at the first round of two-day-long talks that were held behind closed doors.