North Korea said Tuesday that it has completed reprocessing thousands of spent nuclear fuel rods to extract plutonium to bolster its atomic stockpile, raising the stakes in an apparent effort to get the U.S. into direct negotiations.

The North's official Korean Central News Agency said in a dispatch that the country finished reprocessing 8,000 spent fuel rods, which experts say yields enough plutonium for at least one atomic bomb.

The North is believed to already be in possession of enough plutonium to make at least half a dozen nuclear weapons. The latest announcement raises concern that the regime could enlarge its atomic stockpile.

The announcement came a day after North Korea's Foreign Ministry pressured Washington to accept its demand for direct nuclear talks.

North Korea restarted its once-mothballed nuclear facilities at its Yongbyon complex in April in anger over a U.N. rebuke of its rocket launch, which was denounced as a test of its long-range missile technology. It has also kicked out international nuclear monitors before conducting nuclear and missile tests.

In September, the North said it was in the final stage of reprocessing spent fuel rods. The North claimed at the time that it succeeded in uranium enrichment — which would give the communist regime a second way of building atomic bombs.

North Korea has been demanding direct talks with the United States to resolve the nuclear standoff.

Washington has said it is willing to meet one-on-one with the North — if it leads to the resumption of six-party talks involving China, Japan, the two Koreas, Russia and the U.S.

But the U.S. has not made any decision on whether to hold direct talks, prompting Pyongyang to threaten to increase its nuclear arsenal unless its demand is met.