A U.S. think tank says North Korea has moved beyond laboratory-scale work in the development of highly enriched uranium (HEU) and has the capability to build, at the very least, a pilot-scale gas centrifuge plant.

The U.S. Institute for Science and International Security, which promotes nuclear disarmament, said this week in a report that it believes North Korea has so far secured 500 to one-thousand centrifuges.

But it said however that "even if North Korea produced highly enriched uranium, without further evidence, that conclusion does not translate to North Korea having a facility able to produce weapon-grade uranium on a significant scale, such as in a plant with one-thousand to three-thousand centrifuges."