The apparent shutdown of a nuclear reactor in North Korea (search) is raising concerns among Bush administration officials that Pyongyang has completed the task of producing spent fuel rods laced with weapons-grade plutonium.
But a U.S. official familiar with the situation said there could be at least two other possibilities, neither of which is troubling: that the reactor has run into mechanical trouble or that North Korea is bluffing in order to raise anxieties.
In the past, North Korea has claimed to have taken major steps in its pursuit of a nuclear weapons arsenal and only some of those claims are credited by U.S. analysts as genuine. Even so, North Korea is believed to have already produced at least one atom bomb and the United States, China, Japan, South Korea and Russia are trying to negotiate elimination of the nuclear weapons program.
North Korea had agreed to return to the bargaining table last September after a three-month hiatus but since then has refused to resume the so-called six-nation talks.
The shutdown of the reactor in North Korea's main nuclear complex at Yongbyon (search) was detected by what U.S. analysts refer to as "overhead imagery," which could involve spy satellites, but not always.
The idea is to look for cessation of smoke or for significant changes in the readings of thermal or radar counts, said a U.S. official speaking on condition of anonymity.
"This is entirely feasible, but for us to know for sure, we'd have to be physically there ourselves and this is no longer the case," said Melissa Fleming, a spokeswoman for the International Atomic Energy Agency (search).
She confirmed that the reactor would have to be shut down for the fuel rods to be extracted.
In Seoul, meanwhile, Kim Sook, director-general of North American affairs at South Korea's Foreign Ministry, told KBS Radio that a shutdown of a nuclear reactor at the Yongbyon nuclear complex had been confirmed.
Yongbyon houses a 5-megawatt reactor that generates spent fuel rods laced with plutonium, but they must be removed and reprocessed to extract the plutonium for use in an atomic weapon. They can be removed only if the reactor has been shut down.
North Korea restarted the reactor after expelling U.N. monitors at the end of 2002.
"We have to wait and see the intentions and the measures North Korea takes in the future," Kim said.
North Korea's persistent refusal to resume negotiations has provoked behind-the-scenes quibbling among the United States and its partners over bargaining tactics.
But there is a consensus on offering North Korea economic incentives and international acceptance if it would agree to stop developing nuclear weapons.
A U.S. scholar who recently visited North Korea said earlier this month that officials there told him they were preparing to unload fuel rods from the Yongbyon reactor during the next two months, adding to the urgency of resuming nuclear talks.
"They will have more plutonium unless there is a freeze," Selig Harrison, a Washington-based researcher, told reporters in Beijing after his trip.