The communist state said a day earlier that it had completed reprocessing the rods and had started using plutonium to make nuclear weapons as a deterrent against what it calls a U.S. plan to invade. Washington says it has no intention of invading.
"All the technological matters have been solved fully in the process of making a switchover in the use of plutonium," said the North's official news agency, KCNA. It was impossible to independently verify the claim because North Korea has expelled international inspectors from its nuclear facilities.
"The DPRK will maintain and steadily increase its nuclear deterrent force as a self-defensive means to cope with the (United States') ever more undisguised threat to mount a pre-emptive nuclear attack on the DPRK," the North Korean agency said. The DPRK is the acronym for the North's official name, Democratic People's Republic of Korea.
When reprocessed with chemicals, the 8,000 rods can yield enough plutonium to make five or six bombs, according to experts. American intelligence analysts believe North Korea already has at least one or two nuclear bombs.
The North has made similar claims about its nuclear capabilities since the crisis over its nuclear projects started a year ago. It was unclear whether the announcement was a sign North Korea has turned its back on the possibility of giving up its nuclear ambitions or was an attempt to gain leverage ahead of any talks on the matter.
North Korea's neighbors on Friday urged it to back down. Japan reminded North Korea it promised at a multilateral meeting in Beijing that it wouldn't escalate the nuclear standoff.
"Considering that, what the North has done is regrettable," Japanese Foreign Minister Yoriko Kawaguchi said.
South Korean President Roh Moo-hyun called the North's initial statement about the plutonium on Thursday "sort of a bombshell announcement," but he appealed for calm.
"There have been in the past an uninterrupted string of various unexpected outbreaks" in relations between the two Koreas, he said. "But if we react too sensitively, it could only aggravate the already tense situation."
Roh reiterated Friday that concerns over North Korea's nuclear weapons ambitions make it difficult for him to decide to send South Korean troops to help U.S. forces in Iraq.
"What worries me the most is ... a scenario in which I decide to send troops to Iraq and then North Korea takes strong measures, as it has often done in the past, regarding the reprocessing, plutonium, nuclear weapons and missiles, and the situation on the Korean Peninsula worsens rapidly," Roh told reporters.
Senior U.N. envoy Maurice Strong met North Korean Vice Foreign Minister Choe Su Hon for about 30 minutes on Thursday at the United Nations and said Pyongyang was still offering to drop its nuclear weapons program if the United States promises not to attack.
"He made it very clear that his government is committed to abandoning its nuclear weapons program, to subjecting itself to internationally agreed inspections and verification procedures, and that their primary concern is their security," Strong said in New York.
Strong said, however, that Choe reiterated North Korea's stance that the United States' "hostile" posture means the North will continue with its nuclear program.
North Korea said the reactor in its main nuclear complex at Yongbyon, 60 miles north of Pyongyang, was operating normally and will produce more spent fuel rods.
"The reprocessing facility in Yongbyon is fully ready to resume its operation when necessary in the future," KCNA said Friday.
It said the reprocessing of the existing 8,000 spent rods was successfully finished by the end of June. North Korea had made the claim earlier, but U.S. officials have expressed doubts over it.
North Korea may have reprocessed some rods after U.N. inspectors left the country in January, U.S. officials believe, but the number is unclear.
White House spokesman Scott McClellan said Thursday the United States had not confirmed North Korea's claim. "They've made that statement before," he said.
"There's no legitimate use for plutonium harvested during these procedures," McClellan said. "It would be a clear indication that they are intent on enlarging their nuclear arsenal, despite the call from the international community for North Korea to change its behavior."
Choe reportedly told journalists in New York that North Korea has pledged not to export its nuclear capability.
The nuclear dispute flared last October when U.S. officials said North Korea admitted running a secret nuclear weapons program in violation of international agreements.
By Sang-Hun Choe