SEOUL — North Korea’s sudden announcement that it had finished reprocessing 8,000 spent nuclear fuel rods and has begun making atomic bombs was met with caution and concern by South Korean officials and the Bush administration.

An unidentified North Korean Foreign Ministry spokesman made the announcement Wednesday via the North’s official news agency, KCNA.

The North “successfully finished the reprocessing of some 8,000 spent fuel rods,” the North Korean announcement read, according to a translation by The Associated Press.

North Korea “made a switch- over in the use of plutonium churned out by reprocessing spent fuel rods in the direction of increasing its nuclear deterrent force,” the statement also claimed.

And because the United States has taken what Pyongyang characterized as a “hostile policy,” North Korea will reprocess more spent fuel rods to produce more nuclear weapons, the statement claimed.

North Korean Vice Foreign Minister Choe Su Hon echoed the statements in remarks to reporters at the United Nations in New York.

North Korea processed and “changed the purpose of these fuel rods,” China’s Xinhua news agency quoted Choe as saying.

U.S. intelligence analysts are concerned that if North Korea develops more than the one or two nuclear weapons the CIA estimates Pyongyang already has, the North either could test or sell one of the weapons, The Associated Press reported. New atomic weapons also would give the North more authority at the negotiating table, analysts said.

Reprocessing 8,000 rods could yield enough material to create 20 nuclear bombs, scientists have said.

Officials at U.S. Forces Korea did not return several calls Wednesday seeking comment on the report.

Late Thursday, a South Korean Foreign Affairs and Trade Ministry spokesman said the government expressed “utmost regret” at the North’s nuclear announcement.

“North Korea should not take any moves worsening the situation, and we urge it to answer our call for six-way talks immediately,” the spokesman said on condition of anonymity.

South Korean Foreign Ministry spokesman Shin Bong-kil urged North Korea to refrain from any steps that would worsen the situation and to return to the six-nation talks on its nuclear programs.

“We express our concern that this latest North Korean statement could hurt efforts to resolve the nuclear problem peacefully, hurt development of South-North Korean relations and damage the atmosphere of dialogue,” Shin said in a statement.

In Washington, White House spokesman Scott McClellan said the United States had not confirmed the North Korean claim, and said “they’ve made that statement before.”

“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 international community for North Korea to change its behavior.

“We’ve been talking about these issues in the six-party talks, and North Korea has received the message from all these nations that they need to end the nuclear weapons program in a verifiable and irreversible way, once and for all.”

The announcement came just days after North Korean officials said they were “uninterested” in continuing the six-nation talks to defuse the nuclear crisis unless the United States signs a non-aggression pact. The first round took place in Beijing in August; the second was expected this month.

South Korean analysts have said the North likely is issuing the statements as a negotiating tactic.

The announcement could cause more headaches for South Korean President Roh Moo-hyun, who has tied the U.S.-requested deployment of combat troops to Iraq with the resolution of the nuclear standoff.

— The Associated Press contributed to this report.

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