After years of silence, the father of American-born Taliban soldier John Walker Lindh called on President Bush on Thursday to grant clemency to his son, who he says was wrongly maligned as a traitor and murderer.

"In simple terms, this is the story of a decent and honorable young man embarked on a spiritual quest," said Frank Lindh, swallowing back tears at times during a speech at the Commonwealth Club, a nonprofit organization.

Frank Lindh said that although his son had nothing to do with the Sept. 11 attacks, they ended up adding dire consequences to his decision to join the Taliban, targeted by the U.S. after the 2001 attacks for harboring Al Qaeda leader Usama bin Laden.

"Being viewed through the prism of those attacks has caused this young man to be vilified as a terrorist and a traitor," the elder Lindh said.

John Walker Lindh, who turns 25 next month, was 20 when he was captured by American forces on Nov. 21, 2001, alongside Taliban fighters.

Charged with conspiring to kill Americans and supporting terrorists, the younger Lindh avoided a potential life sentence in 2002 by pleading guilty to lesser charges of supplying services to the Taliban in violation of U.S. economic sanctions and of carrying weapons against U.S. forces. In exchange, John Walker Lindh agreed to withdraw claims of abuse or torture.

Until now, his parents have mostly maintained a public silence about the case, hoping to avoid a media barrage that could be detrimental to their son. But on Thursday Frank Lindh shared baby pictures and other photos of his son during the presentation and said he is proud of his child.

Frank Lindh said he decided to break his silence because he hoped the story of his boy's journey from bucolic Marin County to harsh Afghanistan battlefields will help him get a reduction in his 20-year prison sentence. Last year his son renewed his request for clemency, already rejected once.

John Walker Lindh, raised Catholic, was 12 when he saw the movie "Malcolm X" and became interested in Islam, his father said. A few years later he converted to Islam in a mosque in Mill Valley.

With his parents' blessings, he headed to Yemen, and later Pakistan, to memorize the Quran and become an Islamic scholar.

What did Frank Lindh think of his son's decision to pursue these studies?

"It's a wonderful thing for an American kid to go overseas and study, to learn another language, to learn another religion, these are great things," he said.

In the spring of 2001, John Walker Lindh told his parents he was going to dodge the desert heat and spend the summer in the mountains of Pakistan. He did not tell his parents that he planned to cross into Afghanistan and join the Taliban army.

The younger Lindh saw bin Laden speak twice while he was training in Afghanistan, but had no idea that he was involved in terrorism against the U.S., his father said.

On Thursday, Frank Lindh emphasized that John Walker Lindh was involved in an Afghan war, not a fight against the U.S., when the Muslim convert joined the Taliban army to fight the Northern Alliance. He noted that the U.S. once supported Taliban fighters when they were fighting the Soviet occupation of Afghanistan.

"What happened unfortunately for John is that the United States made an abrupt change after the 9-11 attacks," Frank Lindh said. "We switched sides. John was on the ground there when that happened. He certainly didn't go to Afghanistan to do anything against America. He never fought against America. He never fired a gun at an American. He was simply rescued."

Or he thought he had been rescued, his father said, until he was taken into custody, duct taped naked on a stretcher and held in a metal shipping container for two days.

Frank Lindh said he would not have urged his son not to get involved in the fighting had he known of his plans.

"If he had asked, I would have told him, 'John, we don't have a stake in that fight,"' said Frank Lindh. "I would have told him that if he wants to help, he should go work in a refugee camp."

Even so, Frank Lindh said his son did no wrong.

"I feel very proud of my son. He acted with great integrity throughout this entire ordeal. He's a great kid. He has more integrity and more dignity than any politician or any journalist that I've ever met," he said.

As passionately as Frank Lindh is advocating for his son's clemency, there is another father fighting just as hard to extend John Walker Lindh's sentence by getting him convicted of murder or treason.

Johnny Spann is the father of CIA officer Johnny Micheal "Mike" Spann, who was killed in a prison riot after being videotaped speaking with John Walker Lindh.

Johnny Spann is conducting his own investigation into the origins of the riot at the Mazar-e-Sharif prison, where suspected Taliban supporters were held. Spann contends that the uprising began with a planned grenade attack inside the prison building rather than a spontaneous scuffle outside where his son was interviewing prisoners, including Lindh.

Frank Lindh, a San Rafael, Calif. attorney for Pacific Gas and Electric Co., said he and Lindh's mother, Marilyn Walker, an office manager who lives in San Anselmo, visit their son for long weekends each month at the medium security federal penitentiary in Victorville, Calif.

"The silver lining in this whole cloud is that we have wonderful visits with our son," said Frank Lindh. "Ordinarily a son who is 25 doesn't have much time to spend with his father. But we have a lot of time."