North Korea currently has the ability to produce five or six plutonium bombs from 8,000 spent fuel rods in a matter of a few months.

The new step, disclosed by two officials familiar with the North's military activities, could enable the Koreans to build additional weapons in about a year. The administration believes that North Korea now has one or two nuclear weapons.

The disclosure of the new activity came a day after the installation of a new South Korea president, Roh Moo-hyun.

US Secretary of State Colin Powell attended the ceremony and told reporters while en route home Tuesday that the United States was paying close heed to the North's nuclear activities.

He said the North had not restarted either its nuclear reactor or its reprocessing facility. "I think that's a wise choice if it's a conscious choice," Powell said.

The administration learned Wednesday morning that the reactor had been reactivated, said the US officials, asking not to be identified.

One official recalled that the North had said earlier it was going to restart the reactor. He called the move a step in the wrong direction and said it would take the country into further isolation.

When operating, the reactor gives off a plume that can be detected by spy satellites.

The reactor can produce about 13 pounds of plutonium per year. North Korea's weapon designs are estimated to require slightly less than that amount of plutonium for each bomb.

The Bush administration has been attempting to use diplomacy to wean North Korea away from its nuclear weapons program. But Pyongyang has shown no interest.

It has withdrawn from the nuclear Non-Proliferation Treaty, expelled International Atomic Energy Agency monitors and removed the IAEA monitoring equipment. It also has initiated a uranium-based bomb in violation of its international commitments.

The reactor in question is part of a major nuclear complex at Yongbyon, located north of Pyongyang.

On Wednesday, North Korea warned its citizens to prepare for war, saying the country may be the next US target after Iraq. Powell said anew on Tuesday that the United States has no intention of attacking North Korea. He also said all options are on the table.

Earlier in the week, hours before Roh's inauguration, the North tested a short-range missile off its northeast coast. It also threatened recently to abandon the armistice that ended the Korean War 50 years ago.

Peter Brookes, Asian expert at the Heritage Foundation, said Pyongyang "is trying to bring the United States to the negotiating table on terms favorable to North Korea."

Leonard Spector, an arms control expert at the Monterey Institute, said, "Politically, it's one more poke at us, one more provocation."

He said the step is not as serious as restarting the reprocessing plant, which would enable the North to have to have additional nuclear weapons by summer.

(China Daily February 27, 2003)