Washington ? The Supreme Court agreed Friday to decide whether U.S. citizens arrested in America as “enemy combatants” may be held indefinitely without access to lawyers or courts, setting the stage for a major ruling on presidential powers versus civil liberties.

The justices had already agreed to consider the government’s detentions of terror suspects — American and foreign — caught overseas and held incommunicado.

But the case of former Chicago gang member Jose Padilla is seen as the one that will set a key standard as the government pursues the open-ended war on terror: Does the threat of attack justify giving federal authorities unprecedented legal latitude to hold their own citizens?

“The Padilla case is the most significant case for the government,” said Scott Silliman, a Duke University law professor. “The court will have the opportunity to define what it is we call the ‘war on terrorism.”‘

Padilla is one of two American citizens classified as enemy combatants, a term used for captives who are neither traditional prisoners of war nor ordinary criminal defendants. He was arrested nearly two years ago in Chicago after returning from Pakistan. The government alleges he was part of a plot to detonate a radiological “dirty bomb” in the United States.

Atty. Gen. John Ashcroft said that the designation of enemy combatants was “a vital part of the war on terrorism,” that the Supreme Court should reaffirm.

The Padilla case will be argued along with the appeal of the other American charged as an enemy combatant, Yaser Esam Hamdi. He was picked up on the battlefield in Afghanistan.

Lawyers for both men claim their treatment is unconstitutional.