The furore over the photos has shaken the Bush administration (AP/Courtesy The New Yorker) In pictures: Prisoner abuse

Aides have let it be known that Mr Bush was annoyed with Mr Rumsfeld's handling of the crisis over photos showing US troops abusing Iraqi prisoners.

But spokesman Scott McClellan says Mr Bush does not want Mr Rumsfeld to quit.

Observers say pressure on Mr Rumsfeld will only be increased by the new images - one showing a naked man held on a leash by a female soldier.

Resignation calls

The most senior Democrat in the House of Representatives, Nancy Pelosi, said Mr Rumsfeld had been engaged in a "cover-up" of the allegations of abuse and should resign.

She told reporters she did not accept Mr Rumsfeld's repeated assurances that the Pentagon had done enough by investigating the claims of abuse inside the Abu Ghraib jail as soon as they were made, and that the inquiry was announced by officers.

The president greatly appreciates the job that Secretary Rumsfeld is doing White House spokesman Scott McClellan Chaos at Abu Ghraib prison

Tom Harkin, another Democrat, also called for Mr Rumsfeld to quit, becoming the first member of the US Senate to do so.

There has been widespread criticism from US politicians that once the Pentagon knew the scale of the abuse - and in particular that it was depicted in graphic photos which would be broadcast - it did not do more to inform Congressional committees.

President Bush himself said he first saw the photographs of laughing US troops next to Iraqi prisoners in humiliating poses on television.

But when asked if Mr Bush wanted Mr Rumsfeld to remain as head of the defence department, his spokesman replied: "Absolutely".

"The president greatly appreciates the job that Secretary Rumsfeld is doing," Mr McClellan said.

Mr Rumsfeld is likely to face tough questioning about the abuse on Friday when he appears before the Senate Armed Forces Committee along with the US' top military officer, Gen Richard Myers.

New photos

The scandal, which Mr Bush acknowledges has had a "terrible" impact on the US' standing across the Middle East, was fuelled again on Thursday with the publication of more photos.

COALITION-RUN JAILS 8,000 prisoners held in 14 separate jails Three main prisons - Abu Ghraib and Camp Cropper in west Baghdad; Camp Bucca, near Umm Qasr - hold inmates for extended periods Almost all inmates are "security internees"- suspected of posing a threat to the coalition Inmate: 'Treated like dogs' Abu Ghraib abuse report Abuse inquiries under way

As well as the photo of the soldier with a prisoner on a dog leash, another picture released in the US press shows a soldier giving a thumbs-up sign next to what appears to be a corpse.

The Washington Post says it cannot eliminate the possibility that some of the latest images were staged, but reporter Christian Davenport says he believes the pictures are authentic.

He said they were taken in mid-2003 and were scattered among about 1,000 images that also include photos of soldiers posing on camels and general life in the American military in Iraq.

Meanwhile, the International Committee of the Red Cross has said that it repeatedly urged the US to take "corrective action" at Abu Ghraib.

The ICRC, which visits prisoners held by coalition authorities in Iraq, had previously refused to comment publicly on conditions at the prison.

'Dressing down'

The BBC's Justin Webb in Washington says that White House aides have let it be known that Mr Rumsfeld, one of the chief architects of US policy in Iraq, received a dressing-down from President Bush over his handling of the abuse scandal.

The president is said to have been particularly annoyed that no-one told him there were photos of US soldiers posing with hooded or naked Iraqi prisoners until the images aired on national television.

HAVE YOUR SAY The entire sordid saga is an embarrassment Will Martin, Seattle, USA Send us your comments

In a separate development, one of the closest aides of US Secretary of State Colin Powell has made an outspoken attack on other members of the Bush administration.

Larry Wilkerson said Mr Powell had spent much of his time doing damage control around the world for the actions of his colleagues, and attacked those he said were making "cavalier decisions" about sending American men and women out to die.