Monday's developments raise new questions for the administration's North Korea policy, which has come under fire from Democrats and some Korea experts as ill-defined and contradictory.

The Korea experts were separated from the Pakistan experts, who were understandably preoccupied with Mr. bin Laden.

"If things go poorly, you need that resolution as a first step to something more," said Victor D. Cha, a Korea expert at Georgetown University.

Several Korea experts note that in the parlance of the Bush administration, a guarantee against "invasion" is different from a guarantee against a precision attack.

"It really shows that China has changed," said Victor D. Cha, a Korea expert at Georgetown University who is visiting here.

Robert Scalapino, a Korea expert and professor emeritus at the University of California, had played a major role in organizing the trip and was also scheduled to go.

"You let in food," one senior Korea expert in the administration said, describing the memo, "but nothing else."

These analysts say the Bush administration is conspicuously lacking in high-level Korea experts, while Mr. Roh has never been to the United States.

"They will run into this or that problem, just as China once did," said Piao Jianyi, a Korea expert at China's Academy of Social Sciences.

They will want you to bow from the waist, said a Korea expert with whom I breakfasted shortly before leaving for Asia.