US President Bush decided last night to apply the Geneva Convention to Taliban fighters held by the United States but not to al-Qaeda members.
The decision that will not change the captives' treatment but may help protect US soldiers and blunt foreign criticism.
Mr Bush's decision, criticised by some human rights groups, does not confer prisoner of war status on the Taliban detainees, which would have given them protections including the right to disclose only their name, rank and serial number under interrogation and to go home once the conflict is over.
Announcing Mr Bush's move, White House spokesman Mr Ari Fleischer said that as a practical matter the decision would have little effect on the daily treatment of the captives, 186 of whom are detained at the US military base at Guantanamo Bay, Cuba.
The spokesman said the United States had treated the captives humanely and would continue to do so, giving them three meals a day, medical care and the opportunity to worship.
Analysts said Mr Bush's decision may have been designed in part to protect the rights of US soldiers who might be captured in the US military campaign in Afghanistan or elsewhere as Washington prosecutes its war on terrorism.
Some analysts said a motive for not declaring the captives prisoners of war was to ensure the United States could try them before special military tribunals, as distinct from the regular military courts required under the Geneva Convention.
Foreign nations, including close US allies such as Britain and Germany, had expressed misgivings about the Guantanamo Bay captives after the Pentagon released a photograph showing some of them manacled, blindfolded and on their knees.
Britain, which had asked the United States to explain the photographs of the manacled prisoners at Guantanamo Bay, issued a quick statement welcoming Mr Bush's decision.