NEW YORK, Dec 18: In a severe blow to the Bush administration, a US court ruled on Thursday that the president does not have the power to detain as an enemy combatant an American citizen seized on US soil.

In a 2-1 ruling, a three-judge panel of the Second U.S. Circuit Court of Appeals said only the Congress can authorize such detentions and ordered Defence Secretary Donald Rumsfeld to release from military custody Jose Padilla, a US citizen arrested in May last year on return from Pakistan, within 30 days.

The decision could force the Bush administration to try Mr Padilla in civilian courts. He was accused of plotting to detonate a “dirty bomb” in the United States. The government alleged he had proposed the bomb plot to Abu Zubaydah, then Al Qaeda’s top coordinator.

The bomb uses conventional explosives to disperse radioactive material.

Mr Padilla, a former Chicago gang member, was shifted to a naval prison in Charleston, South Carolina, within days of his arrest.

“As this court sits only a short distance from where the World Trade Center stood, we are as keenly aware as anyone of the threat Al Qaeda poses to our country and of the responsibilities the president and law enforcement officials bear for protecting the nation,” the court said in its judgment.

“Presidential authority does not exist in a vacuum and this case involves not whether those responsibilities should be aggressively pursued, but whether the president is obligated in the circumstances presented here to share them with Congress,” the court said.

“Where, as here, the president’s power as commander-in-chief of the armed forces and the domestic rule of law intersect, we conclude that clear congressional authorization is required for detentions of Americans on American soil....” the court ruled.