SEOUL, South Korea – North Korea said Tuesday it has reprocessed 8,000 spent nuclear fuel rods and extracted enough plutonium to bolster its atomic stockpile, raising the stakes in an apparent effort to push the U.S. into direct negotiations.

Reprocessing the spent fuel rods would give the regime enough weapons-grade plutonium for at least one more atomic bomb, experts say. Pyongyang is believed to have enough weaponized plutonium for half a dozen nuclear weapons.

The threat of an expanding North Korean nuclear arsenal comes a day after Pyongyang warned Washington it would beef up its