Throughout January, American spy satellites have detected covered trucks apparently taking on cargo at the nuclear storage facility at Yongbyon, where spent nuclear fuel rods are stored, U.S. officials said Friday on condition of anonymity.
When processed, enough plutonium could be extracted from the rods to make four or five nuclear weapons.
White House spokesman Ari Fleischer would not comment on the intelligence, but warned Pyongyang, North Korea's capital, against taking "another provocative step" that "further isolates North Korea from the international community."
Immersed in planning for a possible war against Iraq, the Bush administration has played down Korean developments of recent months even as North Korea continued to ratchet up the tension.
But there is a broadening consensus in the administration that the reclusive communist regime is moving quickly down the path toward developing nuclear weapons, one senior defense official said. A
At the same time, another said that because North Koreans know they're being watched, Pyongyang is also suspected of maneuvering to force Americans to the bargaining table.
"The fact that they've done this in broad daylight, as it were, suggests to me that this is part of the brinksmanship with the United States," said Kurt Campbell, an Asia specialist at the Center for Strategic and International Studies and a policy adviser at the Pentagon during the Clinton administration.
"I think they're playing with fire," he said. "Even though the administration has feigned nonchalance, the reality is that tampering with plutonium that could be shipped or smuggled is extraordinarily serious, and, I would argue, crosses a very clear and bright red line."
That line may grow even clearer. In response to provocative moves by North Korea, the top U.S. military commander in the Pacific is seeking the deployment of more troops and warplanes, CBS News has learned.
CBS News National Security Correspondent David Martin reports the U.S. commander in the Pacific asked Defense Secretary Donald Rumsfeld for about 2,000 troops, mostly Air Force personnel, to back up the 37,000 already stationed in South Korea.
Two dozen long range bombers – B-52s and B-1s – would be moved to the Pacific island of Guam, in range of targets in Korea. Eight F-15e fighter-bombers plus U-2s and other reconnaissance aircraft would be added to U.S. forces in Japan and Korea.
Officials caution that Secretary Rumsfeld has not yet approved the buildup and that no military action is imminent. But the request for forces is a clear sign the Bush administration is no longer counting on diplomacy alone to handle the building crisis with North Korea.
However, officials say they don't really know what North Korea is up to at the long-shuttered plant, which is north of Pyongyang.
It is possible that the trucks moving there over recent weeks are loading spent fuel rods, either to be stored elsewhere or in preparation for processing, one official said.
More people have been working at the complex, including grading roads, signs that the regime in Pyongyang is resuming operations.
The activity is not particularly unexpected, since the Koreans withdrew from a global anti-nuclear pact and said they would restart the reactor at Yongbyon to generate electricity.
The plant is at the center of the current nuclear dispute. The plant was padlocked under a 1994 deal, in which the United States called off an air strike on the plant and agreed to supply the North with civilian nuclear power plants and fuel aid. In return, the North agreed to stop nuclear development.
This October, the U.S. confronted the North with evidence that it had started a separate, uranium enrichment program. The Bush administration cut off the fuel aid shipments, leading North Korea to declare the 1994 deal dead, expel nuclear inspectors and threaten to restart Yongbyon.
While there is agreement in the intelligence community that North Korea is gearing up at Yongbyon, there is disagreement not only about the ultimate goal but on how far along they've moved, officials said.
Analysts say North Koreans may want the weapons for two reasons: to export for much-needed revenue and to keep for their own use. Also, Pyongyang has been incensed by President Bush's description of the country as part of an "axis of evil" with Iraq and Iran and has demanded assurances it will not be attacked.