Washington has long suspected North Korea of having a program to make highly enriched uranium (HEU) since shortly after it agreed to denuclearize in the first Agreed Framework. North Korea denied this at first, admitted it to two U.S. diplomats and three translators in 2002, and then went back to denying it.
Those denials just got even less likely. As I previously noted here, the U.S. asked for, and North Korea recently provided, samples of aluminum tubes we know it imported. American scientists found traces of enriched uranium on the tubes. HEU atheist David Albright then helpfully offered that if the tubes came from, say, Pakistan, it could actually have been Pakistani HEU we found. Of course, the purchase of tubes from a known proliferator and producer of nuclear weapons/materials is itself suspicious, but never mind that. North Korea says it didn’t get the tubes from Pakistan:
The North acknowledged that it imported 140 tons of aluminum tubes from Russia, apparently intended for use in uranium enrichment centrifuges. It insisted that they had nothing to do with an enrichment program. [Joongang Ilbo]
The report claims to have gotten this information from “diplomatic sources,” probably South Korean. As you’ll see from my previous link above, A.Q. Khan had a global network of supplies and middlemen and used Russian suppliers to deliver aluminum tubes to Iran for its HEU program. Assuming all of these leaks are correct, it is plausible that the tubes came from Russia — or from Pakistan, for that matter. It’s North Korea’s story that still isn’t plausible.