Mr. Siegfried Hecker, former chief of the U.S. Los Alamos National Laboratory, said Saturday that he saw "more than a thousand" centrifuges to enrich uranium and an "ultramodern control room" at a plant at North Korea's Yongbyon nuclear complex when he visited there Nov. 12. North Korea told him and two other U.S. nuclear scientists that 2,000 centrifuges were installed and running.

Pyongyang insists that the purpose of the plant is to enrich uranium for use as fuel for a 25- to 30-megawatt experimental light-water reactor under construction at Yongbyon. But it could be converted into a plant to produce highly enriched weapons-grade uranium. So far, North Korea has been developing nuclear weapons that use plutonium.

With the revelation of the new plant, North Korea may be trying to get the United States to hold bilateral talks and eventually offer rewards to the North in exchange for dismantling the plant. Or it may be trying to use the revelation as a means to bolster the position of Mr. Kim Jong Un, the third son of North Korean leader Kim Jong Il and his heir apparent.