Nuclear test would threaten North Korea's future, warns Seoul

The strong comments came amid growing concern about the North's continued refusal to resume multinational talks on its nuclear aims and after recent US media reports that Pyongyang might be preparing for its first nuclear test.

"If North Korea takes the reckless action of conducting a nuclear test, it will further deepen its isolation and take itself on a road where its future would not be guaranteed," Ban was quoted by Yonhap news agency as telling a forum.

The top US negotiator to the six-party talks also began discussions on Monday in Seoul on how to break the deadlock.

US Assistant Secretary of State Christopher Hill met his South Korean counterpart, Deputy Foreign Minister Song Min-soon. Hill is due to travel to Beijing on Tuesday and Tokyo on Wednesday for further talks.

"What we are focusing on is the diplomatic track and the need to get the talks going and more importantly, once they get going, to achieve progress," Hill told reporters after meeting Song.

Hill said he and Song had a "very good and complete agreement on how to proceed," without elaborating.

Three rounds of the talks by the two Koreas, the United States, Japan, China and Russia have produced no substantive progress. A fourth round never materialised after Pyongyang said Washington must first drop what it called a hostile policy against it.

Arriving in Seoul on Saturday, Hill hinted that his agenda for consultations went beyond just trying to restart the stalled six-country talks, saying officials would try to address "a problem," referring to North Korea's refusal to attend the talks.