The father of the American captured with Taliban fighters said his son was not a traitor but a "very sweet kid" who was the victim of his own bad judgement.
John Walker, 20, could face treason charges, which carry the death penalty, after he was found among 80 Taliban and al-Qa'ida troops who surrendered at the end of a prisoner revolt near Mazar-i-Sharif.
But his father, Frank Lindh, went on United States television to say that his son had gone to help the Taliban before they were at war with America.
Mr Walker could have been confused when he told reporters that as a holy warrior he supported the 11 September attacks, Mr Lindh said. "He even said he was not thinking clearly. It is regrettable that he said what he said, but you have to understand ... this boy had been through a terrible ordeal."
Mr Lindh said he has hired a lawyer and wants to visit Mr Walker, who had studied Arabic and Islam in Yemen and Pakistan. But he also asked for his son to be quickly allowed home to California.
"He's really not much more than a boy," he said. "We want to give him a big hug. I also want to give him maybe a little kick in the butt for not telling me what he was up to and for not getting my permission, because I would not have given him permission to go to Afghanistan."
The US Defence Secretary, Donald Rumsfeld, said that Mr Walker was in custody of US special forces near Mazar-i-Sharif and that his fate had not yet been decided.
Mr Walker would receive all his legal rights, but his case was not a priority, he said.Reuse content