By Matthew Davis BBC News, Washington

Erik Saar says the US treatment of prisoners hurts its moral standing

A former US soldier who worked on interrogations at Guantanamo Bay has written a damning expose of the brutal, degrading treatment he says was meted out to prisoners there.

Sgt Erik Saar's book, Inside the Wire, comes with the US military's treatment of prisoners in the spotlight due to court hearings over the Abu Ghraib prison scandal.

In an interview with the BBC, Sgt Saar says that bizarre, sexual abuses at the prison camp set dangerous precedents that paved the way for mistreatment of US detainees in Iraq.

And the former translator argues that despite attempts to right wrongs at Guantanamo, the camp still defiles the values the US is fighting for in the war on terror.

'Does that please Allah?'

One of the most disturbing interrogations Sgt Saar says he saw in his six months at the prison concerned a female interrogator trying to break a Saudi detainee, captured after enrolling in a US flight school.

'Brooke' came back round his other side, and he could see that she was beginning to withdraw her hand from her pants. As it became visible, the Saudi saw what looked like red blood on her hand Erik Saar 'Inside the Wire'

He tells how she began peeling off her clothes, taunting the man sexually in an attempt to shame him and stop him relying on his faith for support.

She left the interrogation room, Sgt Saar says, and found a red marker pen.

"'Brooke' came back round his [the prisoner's] other side, and he could see that she was beginning to withdraw her hand from her pants," said Sgt Saar.

"As it became visible, the Saudi saw what looked like red blood on her hand."

When the interrogator wiped what he thought was menstrual blood on his face, the prisoner raged, almost breaking free from his handcuffs.

But "Brooke" taunted him further, said Erik Saar, asking whether Allah would be pleased with him and telling him to have fun trying to pray.

Finally the detainee was returned to his cell without water, leaving him unable to cleanse himself.

'Start of a mistake'

Sgt Saar volunteered for Guantanamo in 2002. He was a US Army linguist, an expert in Arabic and had high security clearance.

The Pentagon says its policies on prisoner treatment have not led to abuse

But he says what he saw completely changed his attitude towards the camp, and his country.

There were many more suicide attempts in the camp than the US government has ever admitted, Sgt Saar says.

He claims storm trooper-like IRF (initial reaction force) teams were involved in numerous beatings of captives.

And of the 600 or so prisoners there, no more than a few dozen were "hardcore terrorists", says Erik Saar.

"The US Government portrays Guantanamo as a place where we are sending the worst of the worst, but this is not true.

"Guantanamo was the beginning of a mistake. It set a precedent in labelling people as enemy combatants, blurring the line between right and wrong.

"You can see it as the seed that may well have led to the naked human pyramids in Abu Ghraib."

FBI memos

In December 2004, the American Civil Liberties Union released a slew of material relating to prisoner abuse, obtained via the Freedom of Information Act.

FBI 'torture' email in full Source: American Civil Liberties Union Most computers will open PDF documents automatically, but you may need to download Adobe Acrobat Reader. Download the reader here

This included an FBI email - from December 2003, six months after Sgt Saar left - that said Defense Department interrogators at Guantanamo had impersonated FBI agents while using "torture techniques" on a detainee.

US Southern Command told the BBC it was investigating alleged detainee abuse following the publication of the FBI memos.

But USSC says it will not comment on any abuse allegations until the inquiry report is published.

Officials also deny allegations in Erik Saar's book that interrogations at Guantanamo were "staged" for visiting inspectors.

A spokesman told the BBC that Mr Saar was merely a junior linguist, "not in a position to understand the decisions behind interrogation planning".

'Whitewash'

The US Army is addressing the issue of how to treat a prisoner humanely, while still applying the pressure needed to get them to reveal critical information.

It is poised to issue a new field interrogation manual, which will expressly forbid certain harsh techniques and include detailed examples with references to the Geneva Conventions.

Throwing a chair against a wall in a fit of mock anger may be permissible, for instance, but using the chair to hit the detainee would not.

In March, a Pentagon investigation into the interrogation of prisoners detained in the war on terror found its policy did not lead to abuse.

The review - launched last year - examined 187 Pentagon investigations of alleged abuse in Iraq, Afghanistan and Guantanamo Bay.

Human rights groups criticised the review as a whitewash.

Sgt Saar believes improvements have been made at the camp, but says more radical change is needed, to bring prisoners within the US judicial system.

"People say if what I have written is the worst that went on, it is not too bad," he says.

"But Guantanamo has become a symbol of everything wrong with America's image. If we are trying to build a bridge to the Muslim world, what sort of face are we portraying?"

Inside the Wire by Erik Saar and Viveca Novak is published in the United States by The Penguin Press.