SEOUL, South Korea -- South Korea's top official for relations with North Korea urged Washington and Pyongyang on Thursday to hold direct talks in an effort to restart stalled international negotiations on the North's nuclear weapons program.

Unification Minister Lee Jong-seok indicated there was a high possibility that senior U.S. and North Korean officials would hold one-on-one talks next week on the sidelines of a privately sponsored security conference in Japan.

"Dialogue between the U.S. and North Korea is necessary regardless of format," Lee told reporters at a weekly briefing.

The U.S. Embassy announced on Tuesday that officials from the six countries participating in the stalled North Korean nuclear disarmament talks - the United States, China, Japan, Russia and two Koreas - would meet at the private conference in Tokyo on April 10-11.

North Korea has refused to participate in the six-way nuclear negotiations since last November, demanding that the U.S. first lift sanctions it imposed on a Macau bank and North Korea companies for alleged complicity in counterfeiting and money laundering.

U.S. and North Korean officials met in New York last month but failed to resolve the dispute. North Korea has denied the U.S. allegations, while Washington says the sanctions are a separate issue from the nuclear talks.

In September, North Korea agreed at the six-way talks to abandon its nuclear programs in exchange for aid and security assurances. But follow-up negotiations on implementing the agreement have stalled.

The private conference in Tokyo is sponsored by the University of California Institute on Global Conflict and Cooperation.

North Korea declared last year that it has nuclear weapons, although the claim hasn't been independently confirmed.