US President Barack Obama's decision not to prosecute CIA agents who used torture tactics is a violation of international law, a UN expert says.
The UN special rapporteur on torture, Manfred Nowak, says the US is bound under the UN Convention against Torture to prosecute those who engage in it.
Mr Obama released four "torture memos" outlining harsh interrogation methods sanctioned by the Bush administration.
Mr Nowak has called for an independent review and compensation for victims.
"The United States, like all other states that are part of the UN convention against torture, is committed to conducting criminal investigations of torture and to bringing all persons against whom there is sound evidence to court," Mr Nowak told the Austrian daily Der Standard.
The memos approved techniques including simulated drowning, week-long sleep deprivation, forced nudity, and the use of painful positions.