US Defence Secretary Donald Rumsfeld has said he would like to expedite the processing of prisoners held since the war in Afghanistan.

Few detainees have been released from Guantanamo Bay

He acknowledged getting a letter from Secretary of State Colin Powell concerning the 660 prisoners held at a US navy base in Guantanamo Bay, Cuba.

Some of the prisoners have been held for more than a year and their detention has drawn protests from human rights groups and their own governments.

But Mr Rumsfeld told a US TV network that thorough questioning remained necessary for the detainees, most of whom are suspected members of the Taleban or al-Qaeda.

"It takes time to find out what intelligence they have," he told CNN.

"It also takes time to figure out what law enforcement process might be appropriate.

Mr Rumsfeld said four agencies were involved in questioning

"What Colin and I have been concerned about... is that it's taking so long," he said.

The FBI, Department of Justice, CIA and the Pentagon's Defense Intelligence Agency were all involved in the process of interrogating the detainees, Mr Rumsfeld said.

"The inter-agency process takes a great deal of time. Colin and I are trying speed up that process," he added.

Enemy combatants

Hundreds of people were taken prisoner by US-led forces in the war launched to overthrow the Taleban after the 11 September 2001 attacks on New York and Washington, blamed on al-Qaeda.

The US started moving captives to its remote base in Cuba in January 2002. They have been treated as enemy combatants, not prisoners of war who would have more rights.

None have been charged with a crime and few have been released.

The human rights group Amnesty International has long urged the United States to either charge the Guantanamo prisoners with crimes and try them or let them go.

Three children under the age of 16 are among the detainees, whose status means they have no rights to legal representation.