North Korea has secretly and quickly built a new facility to enrich uranium, according to a US nuclear scientist.
Siegfried Hecker said that he was taken during a recent trip to the North to a plant with a small industrial-scale uranium enrichment facility.
He said it had 2,000 recently completed centrifuges. The North told him it was producing low-enriched uranium meant for a new reactor.
Mr Hecker said his first look at the centrifuges was "stunning" and that the "uranium enrichment facility was ultramodern and clean".
He said the facilities appear to be primarily for civilian nuclear power.
Mr Hecker, former director of the US Los Alamos Nuclear Laboratory and a regular visitor to the North, said he saw no evidence of plutonium production.
But he said the facilities "could be readily converted to produce highly enriched uranium bomb fuel".