His lawyer, James Brosnahan, said Lindh was a young man in the wrong place at the wrong time. He said that Lindh was fighting alongside the Taliban in a civil war against the Northern Alliance, that he is not a terrorist and that he never fought against U.S. troops.
Brosnahan said the sentence should be reduced because Yaser Esam Hamdi, another American citizen captured in Afghanistan on suspicion of aiding the Taliban, is being released after being held for three years as an enemy combatant.
Hamdi will not be charged with any crime under an agreement with federal officials made public Monday. Hamdi will be required to give up his American citizenship and will be sent to Saudi Arabia, where he grew up.
"Comparable conduct should be treated in comparable ways in terms of sentencing," Brosnahan said at a news conference.
The request does not specify how much of a reduction Lindh is seeking.
Lindh's mother, Marilyn Walker, said her son "has never had any sympathy or involvement in terrorist activity."
Lindh, a California native, pleaded guilty in civilian court to supplying services to the now-defunct Taliban government and carrying explosives for them. He and Hamdi were both captured in late 2001.
Brosnahan said he negotiated the 20-year sentence during a time when a "highest state of fear" was affecting U.S. juries and he thought it was the best deal he could get at the time.