North Korea said Friday that it is in the final stages of enriching uranium, a process that could give the secretive nation a second way to make nuclear bombs in addition to its known plutonium-enriching program.

The official Korean Central News Agency said in a report early Friday that North Korea informed the UN Security Council it is forging ahead with its nuclear programs in defiance of international calls to abandon its atomic ambitions.

The dispatch said plutonium "is being weaponized" and that uranium enrichment — a program North Korea revealed in recent months — was entering the "completion phase." Experts had long suspected the existence of a hidden uranium enrichment program, which would give the regime a second source of nuclear material.

The North's announcement came a day after a U.S. special envoy arrived in Beijing for talks with Chinese officials on how to get North Korea back on track with its commitments to nuclear disarmament.

Stephen Bosworth, the special envoy to North Korea, was to arrive in Seoul later Friday for similar consultations with South Korean officials before traveling to Tokyo on Sunday as part of an Asian tour amid recent conciliatory moves by Pyongyang.

His visit to the region aims to "continue consultations with our partners and allies on how to best convince North Korea that it must live up to its obligations … and take irreversible steps toward complete denuclearization," the U.S. Embassy in Beijing said in a statement.

Six-party nuclear talks

North Korea called the decision to push ahead with its nuclear programs a reaction to the Security Council's moves to tighten sanctions against the regime for testing a nuclear bomb in May. Pyongyang labelled the UN resolution a "wanton violation of the [Democratic People's Republic of Korea]'s sovereignty and dignity."

The U.S., China, Japan, Russia and South Korea have been negotiating with North Korea for years on dismantling its nuclear program in exchange for aid and other concessions.

North Korea walked away from the talks earlier this year. North Korea also conducted its second nuclear test in May, drawing international condemnation and new UN sanctions.

The North's move came amid conciliatory overtures to Seoul and Washington. The North freed two U.S. journalists and five South Koreans, including four fishermen, in recent weeks.

The two Koreas also agreed to restart reunions of Korean family separated by the 1950-53 Korean War and restored regular traffic to a joint industrial park in the North.

South Korea's Foreign Ministry spokesperson was not immediately available for comment on the North's latest nuclear claim.