By Year's End, Pyongyang Could Have Material For 20 Nuclear Bombs, Says U.S. Expert

North Korea has developed the ability to build seven nuclear warheads a year beyond its existing stockpile of fissile material for around 20 bombs, according to a top U.S. nuclear scientist cited by the Yonhap news agency (Seoul).

Moreover, Pyongyang will likely be able to build nuclear missiles capable of reaching the United States within a decade, said the expert.

Siegried Hecker, a Stanford University professor who visited North Korea's uranium-enrichment facility in...