The announcement underlined Pyongyang's impatience over securing one-on-one talks with Washington, as well as the difficulties in dealing with a regime that resorts to threats and provocations to get what it wants.

Pyongyang's official Korean Central News Agency said that North Korea had finished reprocessing 8,000 spent nuclear fuel rods, which experts say would provide enough weapons-grade plutonium for at least one more nuclear bomb.

The claim may not mean much, since North Korea is believed to already have enough weaponized plutonium for half a dozen nuclear weapons. But the timing - a day after Pyongyang warned it would beef up its nuclear arsenal if the United States refused to agree on bilateral talks - shows the communist regime is flexing its atomic might to try to push Washington to act, analysts said.

U.S. State Deparment spokesman Ian Kelly accused the Pyongyang government of violating its past commitments at international disarmament talks.

"Reprocessing plutonium is contrary to North Korea's own commitments" at those negotiations and violates U.N. resolutions, Kelly told reporters in Washington. He said the Obama administration was focused on trying to restart stalled six-nation nuclear talks.

North Korea has long sought direct nuclear negotiations with the United States, believing that it is the easiest and fastest way of ensuring the survival of the totalitarian regime and winning economic concessions to rebuild its moribund economy.

On Monday, North Korea's Foreign Ministry warned that "if the U.S. is not ready to sit at a negotiating table with the [North], it will go its own way," an apparent threat to bolster its nuclear arsenal.

Pyongyang has said it needs atomic weapons to defend itself against the United States, which fought against the North during the Korean War in the 1950s and has 28,500 troops stationed in South Korea to protect the ally.

The United States says it has no intention of attacking the North.

But the North said yesterday that it remained "compelled to take measures to bolster its deterrent for self-defense to cope with the increasing nuclear threat and military provocations of the hostile forces."

Washington has said it is willing to meet one-on-one with the North if the talks lead to the resumption of the six-nation negotiations involving China, Japan, the two Koreas, Russia, and the United States.

However, discussions between a North Korean envoy and a U.S. official last week did not yield an agreement to hold talks, both sides said.

Kelly told reporters Monday that Sung Kim, the chief U.S. nuclear negotiator, recently had useful discussions with Ri Gun, North Korea's No. 2 official for nuclear talks. He said the United States was still considering North Korea's offer.