Jose Padilla sketch
© Agence France-PresseJose Padilla (R) and prosecution attorney Stephanie Pell are shown in a sketch during his hearing in Miami in 2006

A US appeals court Tuesday rejected an effort to revive a lawsuit by Jose Padilla, a US citizen arrested in 2002 for an alleged "dirty bomb" plot who claims he was illegally detained and tortured.

The federal appeals court in Richmond, Virginia, affirmed a lower court decision which said former US defense secretary Donald Rumsfeld and current Pentagon chief Leon Panetta are immune from the suit for actions taken in their official capacity.

"The political branches, exercising powers explicitly assigned them by our constitution, formulated policies with profound implications for national security," the appeal panel decision said.

"One may agree or not agree with those policies. One may debate whether they were or were not the most effective counterterrorism strategy. But the forum for such debates is not the civil cause of action pressed in the case at bar."

Padilla, who is incarcerated at a high security jail in Colorado, previously sued in an attempt to hold Rumsfeld and other US officials accountable for his alleged suffering, but a district court judge dismissed the case.

The American Civil Liberties Union (ACLU) claimed in the suit that Padilla was imprisoned without trial for four years and subjected to a range of abuse.

Padilla, a former Chicago gang member and Muslim convert, was convicted in 2007 of aiding a US-based Al-Qaeda cell and was subsequently sentenced to 17 years in jail.

He left the United States in the 1990s to study in Egypt and later traveled to Afghanistan. He was arrested in 2002 as he returned to the United States.

The terror cell was alleged to have supplied recruits and funding to Islamic extremists abroad, and conspired to murder, kidnap and maim people in Afghanistan, Chechnya, Bosnia and other countries from 1993 to 2001.

US authorities justified his detention without charge at a US navy prison in South Carolina by saying he was an "enemy combatant" who had planned to explode a radioactive bomb in the United States.

The ACLU expressed disappointment over the latest ruling.

"Today is a sad day for the rule of law and for those who believe that the courts should protect American citizens from torture by their own government," said the ACLU's Ben Wizner, who argued the appeal in court.

"By dismissing this lawsuit, the appeals court handed the government a blank check to commit any abuse in the name of national security, even the brutal torture of a US citizen on US soil."