Attorneys defending an American accused of participating in an Al Qaeda (search) plot to set off a "dirty bomb" have issued a challenge to federal prosecutors: prove it or free him.

Jose Padilla's (search) attorneys on Wednesday asked U.S. District Judge Henry Floyd to hear their writ of habeas corpus (search), a petition that allows a civilian judge to consider their case. Padilla was not present.

"If everything you say about Jose Padilla is true, prove it," said Denyse Williams, executive director of the American Civil Liberties Union in South Carolina (search), which has filed a brief in support of Padilla's attorneys. "Everybody says the war on terror could last a lifetime. If they can do it to him, they can do it to others."

Padilla was arrested at Chicago's O'Hare International Airport in 2002 after returning from Pakistan. The federal government has said he received weapons and explosives training from members of Al Qaeda.

Padilla, whom President Bush designated an enemy combatant, has been held at the brig at the Charleston Naval Weapons Station for nearly three years. He has not been charged with a crime.

David Salmons from the Solicitor General's Office said Padilla carried an AK-47 with Al Qaeda and Taliban (search) forces in Afghanistan while U.S soldiers were there after the terrorist attacks of Sept. 11, 2001.

Padilla then fled to Pakistan, where he met with Al Qaeda leaders and agreed to return to the United States on a mission to detonate a radiological "dirty bomb," Salmons said.

Jonathan Freiman, one of Padilla's attorneys, said the government's allegations are untrue and based on unreliable witnesses, and that Padilla must be charged or set free. Not doing so could lead to a dangerous precedent of any citizen being held without charges, he said.

Salmons said the president has the right to detain any enemy combatant while the United States is fighting Al Qaeda, but added that there's no risk that the president may round up citizens and detain them.

Bush has only determined two citizens were enemy combatants — Padilla and Louisiana native Yaser Hamdi — and both were connected with groups fighting U.S. soldiers, Salmons said.

Hamdi was held in U.S. solitary confinement for nearly three years after being captured on an Afghan battlefield. He was released in October after the Justice Department said he no longer posed a threat to the United States and no longer had any intelligence value.

In 2003, the 2nd U.S. Circuit Court of Appeals in New York ordered Padilla freed unless the government charged him with a crime. The U.S. Supreme Court, without ruling on the merits of the case, decided the circuit court had no jurisdiction and the case was refiled in South Carolina.

Floyd said he will issue an opinion on Padilla's case in the next 30 to 45 days.