American officials said the modest flow had been dictated mainly by the Afghan military, which has wanted to make sure its guards could handle the new arrivals. But some United States officials say they have also had to reassess the Afghans’ ability to hold more dangerous detainees. They said the detention center at Bagram would probably continue to hold hundreds of prisoners indefinitely. “The idea is that over time, some of our detainees at Bagram  especially those at the lower end of the threat scale  will be passed on to Afghanistan,” one senior military official said last year. “But not all. Bagram will remain an intelligence asset and a screening area.”

Ms. Hodgkinson, the deputy assistant secretary of defense for detainee affairs, acknowledged that the military was holding more detainees at Bagram than it had anticipated two years ago and that the Pentagon had no plan to assist the Afghans with further prison-building. But, she added, “A final decision on the higher-threat detainees has not yet been made.”

And even now, the legal basis under which prisoners are being held at the Afghan detention center remains unclear. Another Defense Department official, who insisted on anonymity because she was not authorized to publicly discuss the issue, said the detentions had been authorized “in a note from the attorney general stating that he recognizes that they have the legal authority under the law of war to hold enemy combatants as security threats if they choose to do so.”

Afghan officials said they were still expecting virtually all of the Afghan prisoners held by the United States  with the possible exception of a few especially dangerous detainees at Guantánamo  to be handed over to them.

A spokesman for the Afghan Defense Ministry, Gen. Zaher Azimi, said, “What is agreed is that all the detainees should be transferred.”