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 after midnight 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.

U.S. Attorney Paul McNulty said prosecutors had a strong case against Lindh but wanted to reserve “limited and very vital resources” for other terrorism cases.

“This is a tough sentence. This is an appropriate punishment and this case proves that the criminal justice system can be an effective tool in the fight against terrorism,” McNulty said.

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.

“This is not Rambo we’re talking about here,” Brosnahan said.

Lindh’s mother, Marilyn Walker, broke down outside the courthouse as she called him an “honest, kind, humble and a loving son.”

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

Monday’s events leaves Zacarias Moussaoui, the Frenchman charged with conspiring with the Sept. 11 hijackers, as the lone marquee defendant awaiting trial on terrorism charges. His trial is to begin at the end of September.

Lindh, 21, entered the courtroom wearing a green prison jumpsuit and offered a quick smile to his parents, older brother and younger sister sitting in the second row.

The judge had planned to hold hearings this week on whether Lindh’s statements to investigators and the news media in Afghanistan should be kept out of his trial.

Ellis, who learned of the plea deal shortly before the hearing began, opened court by discussing arrangements for the hearing before Brosnahan interjected, “There is a change in plea.”

An hour later, Lindh entered his two guilty pleas and ended talks that went so late Sunday that Lindh’s lawyers had to make special arrangements to return to his cell so he could sign off on the deal.

President Bush was told of a possible deal last Thursday, administration officials said.

“I plead guilty,” Lindh told Ellis as he entered his plea to one count of supplying services to the Taliban, Afghanistan’s now-ousted strict Muslim rulers. To the charge of carrying explosives during commission of a felony, Lindh said, “I plead guilty, sir.”

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.

Defense lawyer Tony West said Lindh’s attorneys believed they could have won on eight terrorism-related counts but would have had difficulty defending against charges that he helped the Taliban and used firearms during violent crimes.

“The court finds your plea of guilty to be knowing and voluntary,” Ellis said as Lindh stood erect facing the judge, with two U.S. marshals standing behind him. “The court accepts your plea and adjudges you now guilty.”

Lindh agreed to cooperate “fully, truthfully and completely” in the terrorism investigation. Attorney General John Ashcroft emphasized that cooperation and added, “He will now spend the next 20 years in prison nearly as long as he has been alive.”

Under federal law, Lindh could earn up to three years off his sentence for good behavior, but a judge would have to approve any reduction, Justice Department officials said.

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. Bearded and sporting long hair, he gave a hospital bedside interview to CNN in which he professed support for the Taliban.

Government officials who reconstructed his path from a teen-age convert to Islam in San Francisco’s suburbs to a foot soldier in Afghanistan alleged he trained at an al-Qaida camp and once met Osama bin Laden.

By the time he was returned to the United States, Lindh had short hair and his lawyers and family worked hard to portray him as an average American who loved his country. Outside the courthouse, his father said he was thankful the government dropped the more serious terrorism charges.

“Never once did John say anything against the United States,” said Frank Lindh. The defendant’s sister Naomi, 13, and his brother Connell, 24, both said they still loved their brother.

The deal was not popular with the family of Johnny Micheal Spann, the CIA agent who tried to interrogate Lindh in Afghanistan and was killed shortly afterward in a prison uprising. Lindh’s indictment cited Spann’s death as an overt act in a conspiracy to kill Americans, but was dropped from the plea agreement.

Spann’s mother, Gail, of Winfield, Ala., said the 20-year sentence was not fair to her family.

“I’m sure it is to John Walker’s family, but we don’t think it is to us, of course. As Mike’s mom, I would like for Mike to have had 20 years to live,” she said.

Before accepting the plea, Ellis asked Lindh if he was willing to forgo a trial.

“Yes, sir,” Lindh responded.

The judge then asked Lindh a series of standard questions about his background.

“I attended some college in California as well as Yemen,” Lindh explained.

The judge asked him to speak louder. “Do you feel as though you can make a decision about your future today?” Ellis asked.

“Yes,” responded Lindh, who would be 41 when freed from prison.

As part of the agreement, any profits Lindh might make from telling his story would be turned over to the government, McNulty said.