The justices will consider the case of Jose Padilla, an American citizen, former Chicago gang member and convert to Islam, who was arrested in his home city after a trip to Pakistan.

The government alleges he was part of a plot to detonate a radiological "dirty bomb" in the US.

The Padilla case is a companion to another case the court was already set to hear this spring.

Together, the Yasir Isam Hamdi and Padilla cases will allow the court to take its most comprehensive look so far at the constitutional and legal rights of Americans caught up in the global "war on terror".

Lawyers for both men claim their treatment is unconstitutional. Hearing the cases together will simultaneously address the rights of US citizens captured abroad and at home.

Unfettered powers

At issue is the president's claim of authority to pursue terrorists unfettered by many traditional legal obligations - and outside previous precedents for government conduct in wartime.

The Supreme Court is expected to hear both cases in late April, with a ruling due by summer.

Separately, the court will hear a challenge this spring from foreign-born "terror suspects" held in open-ended custody at the military's prison camp at Guantanamo Bay, Cuba.

That case asks whether those more than 650 prisoners may challenge their detention and treatment in US courts.

Critics in the US and abroad have argued that the prolonged detentions violate basic human rights and international agreements. A ruling in the Guantanamo case is also expected by summer.