He wrote in his 2006 memoir that Khan transferred nearly two dozen centrifuges — the main equipment used for uranium enrichment — to North Korea, as well as nearly 18 tons of materials, including centrifuges, components and drawings, to Iran and Libya.

Khan also "provided North Korea with a flow meter, some special oils for centrifuges, and coaching on centrifuge technology, including visits to top-secret centrifuge plants," Musharraf wrote in "In the Line of Fire."

In addition, North Korea bought 150 tons of aluminum tubes from Russia, another material used to build the centrifuges required to enrich uranium, said Lee, of the Science and Technology Policy Institute.

In 2007, then-U.S. nuclear envoy Christopher Hill said Washington knew Pyongyang had purchased equipment only used for uranium enrichment.

The future of nuclear disarmament negotiations with North Korea — known as the six-party talks and involving the two Koreas, the U.S., Russia, China and Japan — remained unclear weeks after North Korea abandoned the process and vowed to restart its plutonium reprocessing plant.

The decision to reveal its capability to enrich uranium now is most certainly tied to the succession campaign believed under way in North Korea, said Cheong Seong-chang, a senior analyst at Sejong Institute security think tank.

The country is in the middle of a "150-day battle" to build up the country's economy; many see it as a political campaign for Kim Jong Un, the 26-year-old reportedly slated to succeed his father, 67-year-old leader Kim Jong Il.

"Uranium enrichment can be used as a propaganda campaign to show Kim Jong Un's boldness as well as the North's determination not to buckle under pressure and solve its energy shortages, Cheong said.