Based on what appears to be a successful test of an atomic bomb more powerful than the one North Korea detonated in 2006, former U.S. government and independent analysts say the North's technical skills are improving slightly.
Of greater concern, according to national security adviser James L. Jones, is the possibility that North Korea could sell or share its nuclear technology with others. He would not say whether the U.S. intelligence community judged the test to be a significant step forward.
"The fact that they have this kind of technology and are obviously willing to export it is very troubling," Jones told reporters Tuesday.
The U.S. government remains officially mum on technical details about the underground blast that took place Monday in North Korea. It could be days or weeks before radioactive gases from the underground test are detected and analyzed by U.S. and allied intelligence.
North Korea appears to be marginally closer to having both a nuclear warhead and the means of delivering it to the United States or U.S. allies in the Pacific. In April, Pyongyang launched a long-range missile in what represented a modest improvement over earlier missile tests. The government reported launching a series of short-range missiles on Tuesday. Read more.