North Korea says it is making progress in producing enriched uranium for its light-water nuclear reactor, raising fresh concerns that the controversial project could be used to develop atomic weapons.

A North Korean Foreign Ministry spokesperson said Wednesday that the country's “experimental” uranium enrichment program is “progressing apace.”

North Korea unveiled its low-enriched uranium plant a year ago at its atomic complex in Yongbyon, saying it would be used to generate electricity.

But some Western observers fear the facility could easily be converted to produce highly-enriched uranium that can be used in nuclear bombs.

U.S. Secretary of State Hillary Clinton said Wednesday at an aid conference in the South Korean city of Busan that Pyongyang should continue efforts to abandon its nuclear program and improve relations with South Korea.

But the North said Wednesday that its right to “peaceful nuclear energy” is a matter of national sovereignty, and that “neither concession nor compromise should be allowed.”

Two years ago, North Korea abandoned talks with the U.S., South Korea, Japan, China and Russia aimed at convincing Pyongyang to dismantle its nuclear weapons program in return for economic and diplomatic benefits.

The North has in recent months pressed to resume the talks without preconditions, but Washington and Seoul say Pyongyang must first shut down its uranium enrichment program and take other steps to demonstrate its sincerity.

North Korea already possesses a plutonium-based nuclear stockpile that is estimated to be capable of producing several atomic bombs.