The main US nuclear envoy said Monday that North Korea was making a terrible mistake by boycotting international disarmament talks as he arrived in Seoul for meetings with top South Korean officials on the deadlocked negotiations. "What they are doing is not in their interest," US Assistant Secretary of State Christopher Hill told reporters, referring to North Korea's refusal to attend the nuclear talks. "Sometimes, small countries can make terrible mistakes. That's really what they are doing," he said. "They are causing a lot of difficulties and really disturbing harmony in the whole region." Hill said that the North should instead return to the six-party talks and that it would find the other countries - China, Japan, Russia, South Korea and the US - prepared to implement an agreement reached nearly a year ago where Pyongyang promised to abandon its nuclear program in exchange for aid and security guarantees. Hill's stop in Seoul is part of his Asian tour that also took him to Japan and China for similar consultations on the North.