A Pentagon spokesman, Lt. Col. Todd Vician, said Sunday that the military disputes Mr. Padilla’s accusations of mistreatment. And, in court papers, prosecutors deny “in the strongest terms” the accusations of torture and say that “Padilla’s conditions of confinement were humane and designed to ensure his safety and security.”

Image In the videotape, Mr. Padilla's feet were shackled.

“His basic needs were met in a conscientious manner, including Halal (Muslim acceptable) food, clothing, sleep and daily medical assessment and treatment when necessary,” the government stated. “While in the brig, Padilla never reported any abusive treatment to the staff or medical personnel.”

In the brig, Mr. Padilla was denied access to counsel for 21 months. Andrew Patel, one of his lawyers, said his isolation was not only severe but compounded by material and sensory deprivations. In an affidavit filed Friday, he alleged that Mr. Padilla was held alone in a 10-cell wing of the brig; that he had little human contact other than with his interrogators; that his cell was electronically monitored and his meals were passed to him through a slot in the door; that windows were blackened, and there was no clock or calendar; and that he slept on a steel platform after a foam mattress was taken from him, along with his copy of the Koran, “as part of an interrogation plan.”

Mr. Padilla’s situation, as an American declared an enemy combatant and held without charges by his own government, was extraordinary and the conditions of his detention appear to have been unprecedented in the military justice system.

Philip D. Cave, a former judge advocate general for the Navy and now a lawyer specializing in military law, said, “There’s nothing comparable in terms of severity of confinement, in terms of how Padilla was held, especially considering that this was pretrial confinement.”

Ali al-Marri, a Qatari and Saudi dual citizen and the only enemy combatant currently detained in the United States, has made similar claims of isolation and deprivation at the brig in South Carolina. The Pentagon spokesman, Lieutenant Vician, said Sunday that he could not comment on the methods used to escort Mr. Padilla to the dentist. Blackened goggles and earphones are rarely employed in internal prison transports in the United States, but riot gear is sometimes used for violent prisoners.