The government and the United States have urged North Korea to stop operating its Yongbyon nuclear reactor.

Song Min-soon, Seoul's chief delegate to the six-way talks, told reporters in Beijing Thursday that Pyongyang must expedite efforts for its nuclear dismantlement.

U.S. chief negotiator Christopher Hill said before the general session that the North should halt reprocessing activities at Yongbyon, adding he hopes to see disclosure of its nuclear facilities and program.

The two officials are seen to have urged the North to implement trust-building measures before the six parties agree on the implementation for the joint agreement reached in the last round of talks.

The fifth round of the talks opened Wednesday in Beijing for a three-day run.