US nuclear envoy Stephen Bosworth sought during his visit to Seoul to convince leaders that the US would act firmly to try to bring North Korea to terms.
The revelation of the project at the Yongbyon complex, revealed by US nuclear physicist Siegfried Hecker after a visit there, means that North Korea is nearing the stage at which it can produce enriched uranium for either electrical energy or warheads.
North Koreans told Mr. Hecker and Charles "Jack" Pritchard, a former US nuclear envoy who also visited the facility, that it was the lightwater kind, solely to produce energy, but analysts doubt that claim in view of North Korea's record of producing materiel for nuclear warheads with plutonium at their core at the same complex.
North Korea's evident success so far in the uranium project means that it will soon have a second reactor that's capable of making warheads quite rapidly once North Korean scientists and engineers have perfected the technology. They're believed to be using components acquired from outside the country despite UN sanctions imposed after the North's second underground nuclear test in May 2009.
The nuclear expert from Stanford who toured North Korea's Yongbyon nuclear facility with US nuclear physicist Siegfried Heckerv has described his shock at seeing the facility.