Three senior US generals will appear before senators today to explain what they knew about the abuse of Iraqi prisoners by soldiers under their command.

The Senate Armed Services Committee will hear evidence from General John Abizaid, the head of US Central Command, Lieutenant General Ricardo Sanchez, commander of ground troops in Iraq and Major General Geoffrey Miller, the deputy commander of prison operations.

Their appearance coincides with the first military trials in Baghdad of soldiers accused of abusing Iraqi prisoners at Abu Ghraib prison.

The officer who was in charge of guards at Abu Ghraib has said that the US military delayed investigating Red Cross reports into abuses for two months and tried to curtail access by the humanitarian group to sensitive cellblocks.

Brigadier General Janis Karpinski, who has already been disciplined over the abuses, told The New York Times that senior US officers treated the International Committee for the Red Cross (ICRC) report in "a light-hearted manner" and generally disbelieved its findings.

A furious row has broken out in Congress over the high-profile abuse hearings on Capitol Hill, which have thrust defence chiefs and soldiers into the spotlight.

Republican Congressman Duncan Hunter has criticised the Senate Committee for continuing with the hearings, which he says are keeping the damaging prisoner abuse story in the news while troops were still risking their lives in Iraq.

Mr Hunter, the chairman of the House Armed Services Committee, said the Senate committee was "basically driving the story" of prisoner abuse and "jerking out these battlefield commanders" while their troops are in a shooting war.

"The Senate has become mesmerised by cameras" and "they have given now probably more publicity to what six people did in the Abu Ghraib prison at 2.30 in the morning than the invasion of Normandy," he added.

But John McCain, the Republican Senator, said that the hearings needed to continue because the abuses have had a direct impact on support for the US-led war in Iraq.

Mr McCain and Republican Senators Lindsey Graham and Susan Collins have been among the most aggressive questioners of witnesses in the hearings, which followed publication of photographs appearing to document abuse at Abu Ghraib prison near Baghdad.

Questions over the behaviour of US troops extended to Afghanistan today, with the announcement that a General will conduct a "top to bottom" review of about 20 US prisons amid growing allegations of prisoner abuses there.

The general, who remains unnamed, will report to Lieutenant General David Barno, the commander of US forces in Afghanistan, by the middle of June.

Some of his findings will be made public, a US military spokesman said.

"He will also ensure all facilities are adequate, and procedures are in accordance with the spirit of the Geneva Conventions and are being followed correctly and fully, and that staffing and capabilities are adequate to the task," the spokesman said.

The US military announced last week that two new investigations into allegations of mistreatment by former Afghan detainees, including beatings and sexual abuse, after coming under intense scrutiny due to the scandal over prisoner abuse in Iraq.

But it has resisted calls from the Afghan Independent Human Rights Commission and the media for access to the jails to see if abuses had been taking place. The ICRC has only visited the main Bagram prison, north of Kabul, and its reports remain confidential.

The US military is also facing criticism for a lack of progress from criminal investigations into the deaths of three prisoners in Afghanistan in 2002 and 2003. Military autopsies found that two had died as a result of "blunt force injuries".

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