Alexandria, Va. ? John Walker Lindh, the young convert to Islam who left California to fight alongside the Taliban, pleaded guilty to two felonies Monday in a surprise deal that spares him life in prison and ensures his cooperation with terrorism investigators.

Lindh faces a maximum of 20 years in prison under the agreement struck between prosecutors and defense lawyers after a weekend of negotiations that ended in the early morning hours of Monday just hours before he was set to appear for court hearing.

“I provided my services as a soldier to the Taliban last year from about August to November,” Lindh told U.S. District Judge T.S. Ellis III, recounting the two crimes to which he pleaded guilty.

“During the course of doing so I carried a rifle and two grenades. And I did so knowingly and willingly,” he added.

In accepting the plea, prosecutors foreclosed the chance for the public to see evidence in the first major trial scheduled from the war on terrorism.

Chief defense lawyer James Brosnahan said Lindh joined the Taliban because he was a devout Muslim. He never fired his rifle and never intended to hurt Americans, the lawyer said.

Lindh was set to be tried Aug. 26, and now will be sentenced Oct. 4.

Each side had its reasons for the deal.

A government official, speaking on condition of anonymity, said the Bush administration was concerned that if the case went to trial, intelligence officers would have to appear and al-Qaida and Taliban detainees held by the United States in Cuba might be allowed to testify for the defense.

Pentagon spokeswoman Victoria Clarke said as part of the deal, Lindh agreed to “cooperate on any future intelligence and information gathering” with his knowledge about the Taliban and al-Qaida.

Lindh came to public attention in December when he was captured with other Taliban prisoners during the war with U.S. military.