SAN FRANCISCO - The lawyer and parents of John Walker Lindh, the American-born Taliban soldier serving 20 years in prison after his capture in Afghanistan, called on President Bush on Wednesday to commute his sentence and set him free.

The renewed call to shorten the sentence was based on the relatively light term Australian David Hicks received Saturday after pleading guilty to supporting terrorism. Hicks, who had been imprisoned for five years at Guantanamo Bay and acknowledged aiding al-Qaida during the U.S.-led invasion of Afghanistan, was given a nine-month sentence.

"In the atmosphere of the time, the best John could get was a plea bargain and a 20-year sentence," said Lindh's father Frank Lindh. "We love our son very much, he was wrongly accused when he was found in Afghanistan."

John Walker Lindh, 26, a Marin County native, was captured in Afghanistan in November 2001 by American forces sent to topple the Taliban after the Sept. 11 terrorist attacks. He was charged with conspiring to kill Americans and support terrorists but pleaded guilty in 2002 to lesser offenses of supplying services to the now-defunct Taliban government and carrying explosives for them.

Attorney James Brosnahan brokered the plea deal and said it was the best he could do amid the political climate immediately after Sept. 11.

Lindh had converted to Islam and went to Afghanistan to fight for the Taliban against the Northern Alliance, Brosnahan said.

"It is a question of proportionality, it is a question of fairness and it is a question of the religious experience John Walker Lindh had and it was not in any way directed at the United States," Brosnahan said at a press conference Wednesday.

The White House referred telephone calls to the Justice Department, which declined to comment because it had not received the petition, said spokesman Dean Boyd.

Neither the president nor the department have acted on two previous commutation requests.