N. Korea's Nuclear Success Is Doubted

But the administration's assessment rests on meager fresh evidence and limited, sometimes dated, intelligence, according to current and former U.S. and foreign officials.

Outside the administration, and in some quiet corners within it, there is nothing close to a consensus that North Korean scientists have succeeded in fabricating atomic bombs from plutonium, as the CIA concluded in a document made public last month.

Independent experts and some U.S. officials also are skeptical of administration claims that North Korea is within months of manufacturing material for more weapons at a secret uranium-enrichment plant.

Interviews with more than 30 current and former intelligence officials and diplomats in Asia, Europe and the United States provide an in-depth look at the development of North Korea's nuclear program, the regime's elaborate efforts to conceal it and the behind-the-scenes debate over how much danger it poses.

According to these officials:

* The U.S. has failed to find the North Korean plant that the Bush administration says will soon start producing highly enriched uranium.

* North Korea's attempts to reprocess plutonium recently hit a roadblock, raising new questions about its technical capabilities.

* China rushed 40,000 troops to its border with North Korea last summer after the U.S. warned that the regime of Kim Jong Il might try to smuggle "a grapefruit-size" quantity of plutonium out of the country. No signs of smuggling have been discovered.

The doubts about U.S. intelligence come as the administration engages in a high-wire diplomatic battle over its demand that North Korea dismantle its nuclear program and open the country to inspectors.

Six-country negotiations aimed at resolving the nuclear crisis could resume later this month or early next year. In what some see as a bid for backing from the other parties -- China, Japan, Russia and South Korea -- the U.S. has portrayed North Korea as a global threat.