The US has released hundreds of pages of previously secret documents which it says show permission was never given to torture military prisoners.
The US has been criticised over conditions at Guantanamo Bay
They suggest that aggressive policies set out by some administration lawyers were rejected by the Pentagon.
BBC Washington correspondent Justin Webb says the documents might go some way towards reassuring the US public.
But he adds that they do not fully address allegations that abuse in Iraq was tacitly encouraged from the top.
A series of photographs depicting abuses at Abu Ghraib prison in Baghdad has provoked worldwide outrage, prompting this release of documents.
Among the paperwork is a directive from President George W Bush which talks of the need for new thinking in the law of war, but insists that all people detained as part of the fight against terrorism should be treated humanely.
Rejected policies included some that appeared to offer a more permissive definition of torture.
A Department of Justice memo from August 2002 argues that
the torture and even deliberate killing of prisoners could be justified as necessary to protect the
The memo from the then Assistant Attorney General, Jay Bybee, says that only actions causing severe pain akin to organ failure would constitute torture.
The papers also show that the Pentagon gave approval - subsequently withdrawn - for interrogation methods at the US naval base at Guantanamo Bay in Cuba which went beyond what was previously considered acceptable.
Some of the methods outlined are reminiscent of Abu Ghraib
Hundreds of suspected al-Qaeda detainees are held at the base.
Defence Secretary Donald Rumsfeld's November 2002 memo approved several methods which apparently would violate Geneva Convention rules, including:
putting detainees in "stress positions" for up to four hours;
- removing their clothes;
- intimidating them with dogs;
- interrogating them for 20 hours at a time;
- forcing them to wear hoods;
- shaving their heads and beards;
- using "mild, non-injurious physical contact" such as
Less than two months later, Mr Rumsfeld withdrew approval for those methods, reportedly on advice from military lawyers. He
appointed a Pentagon panel to recommend interrogation methods.
Prisoners at Abu Ghraib prison were interrogated for as long as
20 hours at a time, kept hooded and naked, intimidated with
dogs and forcibly shaved.
But the Bush administration says other actions - such as forcing prisoners to perform sex acts, beating them and piling them in a naked human pyramid - were unquestionably illegal.
That Pentagon panel appointed by Mr Rumsfeld reported in April 2003. Its recommendations included prohibiting the removal of clothes, which it said could be considered inhumane treatment under international law.
Mr Rumsfeld then issued a new set of approved interrogation methods, banning nakedness and requiring approval for four
techniques - use of rewards or removal of privileges; verbally attacking or insulting the ego of a detainee; alternating friendly and unfriendly interrogators; and isolation.
The administration has insisted that prisoners at Guantanamo Bay are not protected by the Geneva Conventions on prisoners of war because they violated the laws of war themselves.
But Mr Bush and Mr Rumsfeld have said the Geneva Conventions apply to all prisoners in Iraq.
Despite this, Mr Rumsfeld acknowledged last week that he ordered a
suspected terrorist to be secretly held in Iraq without notifying the International Committee of the Red Cross - a violation of the Geneva Conventions.
Mr Rumsfeld also said he had approved an unspecified number of other secret detentions.
Six American soldiers face criminal charges for abusing Iraqi prisoners at Abu Ghraib. Another soldier has pleaded guilty and received a one-year prison term.
The US justice department has filed criminal assault charges against a contract CIA interrogator, accusing him of beating a prisoner in
Afghanistan who later died.