A North Korean nuclear envoy said Friday she held an informal meeting with her U.S. counterparts on the sidelines of a security conference here, where long-standing tensions over the North's nuclear ambition top the agenda.

Choe Son-hui, the North's deputy chief envoy to the six-party talks, told Yonhap News Agency she met with U.S. representatives on Thursday evening during the two-day Northeast Asia Cooperation Dialogue (NEACD) conference that ends Friday.

Asked whether she met with the U.S. side on Thursday, Choe replied, "I met." She did not elaborate further, but a diplomatic source here said Choe held a "casual meeting" with Clifford Hart, the U.S. envoy for the six-nation talks on the North's nuclear program.

Han Song-ryol, the North's deputy ambassador to the United Nations, also attended the 30-minute meeting between Choe and Hart, according to the source.

Organized by the University of California Institute on Global Conflict and Cooperation, the NEACD has served as an opportunity for informal dialogue between North Korea and its nuclear negotiation partners.

For the first time since 2009, senior officials from the six nations involved in stalled six-party talks gathered at the annual security conference.

On Thursday, Seoul's foreign ministry spokesman Cho Tai-young told reporters that South Korea's deputy chief nuclear envoy, Lee Do-hoon, had "no plan" to hold a one-on-one meeting with Choe on the sidelines of the forum.

The six-party talks were last held in late 2008 and diplomatic efforts to resume negotiations have been frozen since April, when North Korea defiantly launched a long-range rocket that failed moments after lift-off. (Yonhap News)