The North, which wants one-on-one talks with the US, said it's open to dialogue and had entered the "completion phase" of developing highly enriched uranium.
North Korea's notice to the United Nations Security Council that it's on the verge of developing nuclear warheads with highly enriched uranium appears as a grab for the attention of the US and other major powers. The North's expertise in uranium would mark a significant escalation of its potential as a nascent nuclear power.
North Korea's UN mission confirmed that the North's UN ambassador, Sin Son-ho, had sent the letter in response to sanctions imposed by the Security Council on June 12, 18 days after the North conducted its second underground test of a plutonium bomb on May 25.
The announcement comes as Stephen Bosworth, the US envoy to North Korea, is visiting the region for talks with North Korea's neighbors. He told reporters in Beijing that the North's claim was "of concern," but he has no plans to visit Pyongyang.
History of boasting
The secretive regime has long boasted of producing plutonium for warheads at its complex at Yongbyon, 60 miles north of the capital Pyongyang, but was believed to be only in the early phases of developing highly enriched uranium.