A federal appeals judge said Monday it would be "a sea change" in the Constitution to allow the Bush administration to designate a U.S. citizen suspected in an alleged dirty bomb plot as an enemy combatant (search).

In a critical showdown between the government and civil rights lawyers, two members of a three-judge federal panel seemed hesitant to embrace the government's reasoning for why Jose Padilla (search), 33, should be held indefinitely without access to a lawyer and without being charged.

Padilla, a Muslim, is accused of plotting with Al Qaeda to detonate a "dirty bomb," which uses conventional explosives to disperse radioactive materials. The former Chicago gang member was taken into custody in May 2002, and has spent most of the time since then in a naval brig in Charleston, S.C.

In the two-hour hearing before the appeals panel Monday, Deputy Solicitor General Paul D. Clement suggested that the urgency of the war against terrorism necessitated such moves.

"Al Qaeda made the battlefields the United States and they've given every indication they're trying to make the United States the battlefield again," he said.

The hearing marked the first time a U.S. government official has said a limited number of enemy combatants could eventually have access to an attorney. Clement told the judges that combatants such as Padilla -- a U.S. citizen being held on U.S. soil -- could get a lawyer once their value as intelligence sources has been exhausted.

But Judge Barrington D. Parker Jr. said he believed the power to designate a U.S. citizen as an enemy combatant rested with Congress, rather than the president.

Giving such power to the executive branch with only limited review by the courts, he said, would be "a sea change in the constitutional life of this country and ... unprecedented in civilized society."

Said Judge Rosemary S. Pooler, another member of the panel: "If, in fact, the battlefield is the United States, I think Congress has to say that, and I don't think they have yet." Later, she added, "As terrible as 9/11 was, it didn't repeal the Constitution."

Specifically, the government was asking the court to overturn a finding by U.S. District Court Chief Judge Michael Mukasey that Padilla is entitled to meet with his lawyers and contest being designated as an enemy combatant.

Jenny Martinez, a Stanford Law School professor who argued on Padilla's behalf, said the government believed it could designate anyone, even a citizen, an enemy combatant at any time.

"This new power government is looking for is entirely unprecedented," she said.

The third judge on the panel, Richard C. Wesley, suggested the case shouldn't have been brought in Manhattan. "This should be litigated in South Carolina," Wesley snapped.

The judges weren't expected to issue their ruling for weeks if not longer. While two of three judges expressed doubts about the government's arguments, they could still opt to refer the case to another court, as Wesley suggested.

Padilla was arrested at Chicago's O'Hare airport as he returned from Pakistan. The government said he had proposed to Abu Zubaydah (search), then Al Qaeda's top terrorism coordinator, to steal radioactive material to detonate a dirty bomb in the United States.

Only two other people have been designated enemy combatants since the 2001 terrorist attacks: Ali Saleh Kahlah Al-Marri, a citizen of Qatar who has been accused of being an Al Qaeda sleeper agent, and Esam Hamdi (search), a Louisiana native captured during the fighting in Afghanistan.