If he is right, that means the United States knowingly allowed an F.B.I. agent to perjure himself at a federal trial of a member of Al Qaeda in New York in February. In his testimony, the agent described in detail how he received computers, hard drives, documents and other material from the SEAL team members immediately after they landed at a base in Afghanistan. He then spent 17 hours cataloging the material before it was put on a plane back to the United States.

The detail, if manufactured, is stunning: The agent, Alexander Otte, listed the types of materials he had received, including the size of some of the digital storage devices recovered (a two-gigabyte micro-SD card, a four-gigabyte thumb drive), and even the brands of the devices (Sony and Kingston).

Mr. Otte also testified that he saw the body of Bin Laden, which Mr. Hersh reported had been largely dismembered by gunfire during the raid. The SEAL team members then threw some body parts out of the helicopters on the way back to Afghanistan, Mr. Hersh writes, though he did report that Bin Laden’s head was largely intact.

Mr. Otte, in his testimony, offered a very different account: Asked if the SEAL team members had a body with them, he said, “It was the body of Osama bin Laden.” At no point did he describe the body as being in pieces or having been decapitated.

Mr. Hersh is standing by his article. In a brief telephone interview on Monday, he said, “You can have your skepticism.”

His manner was cheerful and breezy, and he seemed unfazed about the controversy his reporting has stirred up. It is not the first time that Mr. Hersh’s work has been met with hostility from the authorities, and he laughed loudly at the mention of the denials from the White House and others.

“Those are classic nondenial denials,” he said, before rushing off to take a call from another reporter.