Washington - US President Barack Obama has dropped previous policy of labeling Guantanamo Bay detainees as "enemy combatants," instead holding them under authority provided by Congress and under international law, the Justice Department said Friday.

In a document filed in federal court, the Justice Department broke with the predecessor Bush administration, which argued that the president had sole legal discretion as commander-in-chief to order detention of captives in the war on terrorism.

The Obama administration will now hold detainees found to have planned or participated in terrorist attacks, or to have provided to the Taliban or al-Qaeda "substantial support," a term the Justice Department did not define but said will be determined on a case-by- case basis.

"As we work towards developing a new policy to govern detainees, it is essential that we operate in a manner that strengthens our national security, is consistent with our values and is governed by law," Attorney General Eric Holder said. "The change we've made today meets each of those standards and will make our nation stronger."

The continued detention of detainees at Guantanamo Bay will now be governed by international law and congressional legislation authorizing military force in Afghanistan shortly after the September 11, 2001, terrorist attacks.

The legislation, however, already recognized the president's power to hold prisoners, meaning the shift by the Justice Department announced Friday is mainly symbolic and will have little practical effect.

The American Civil Liberties Union said the decision took only a "half step" toward correcting Bush's policies.

"It is deeply troubling that the Justice Department continues to use an overly broad interpretation of the laws of war that would permit military detention of individuals who were picked up far from an actual battlefield or who didn't engage in hostilities against the United States," said ACLU director Anthony Romero.

The Justice Department said as it conducts the ongoing review of detention policies at Guantanano, it reserves the right to refine the basis for holding detainees at a later date.

Former president George W Bush declared his right to hold detainees as enemy combatants without providing them "prisoner of war" status under the Geneva Conventions. That position had been challenged in federal courts.

Days after taking office in January, Obama ordered the closure of the controversial Guantanamo prison camp within one year and ordered a review of the remaining 245 detainee cases. (dpa)