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Defense Secretary Donald H. Rumsfeld (search) defended military interrogation techniques (search) in Iraq on Wednesday, rejecting complaints that they violate international rules and may endanger Americans taken prisoner.

Rumsfeld told a Senate committee that Pentagon (search) lawyers had approved methods such as sleep deprivation and dietary changes as well as rules permitting prisoners to be made to assume stress positions.

Gen. Richard Myers, chairman of the Joint Chiefs of Staff (search), also noted that the rules require prisoners to be treated humanely at all times.

But Sen. Richard Durbin, D-Ill. said some of the approved techniques "go far beyond the Geneva Convention," (search) a reference to international rules governing the treatment of prisoners of war.

Rumsfeld spoke after two weeks of controversy provoked by photographs of American military personnel abusing prisoners in Iraq. An American was beheaded in a videotaped execution posted to a militant Islamic web site on Tuesday — a killing that captors said was revenge for the abuse of Iraqis in the Abu Ghraib (search) prison.

With lawmakers were immersed in the flap surrounding the pictures of abuse at the prison formally run by Saddam Hussein, President Bush declared there was "no jsutification" for the beheading of an American civilian in Iraq.

He said the terrorists who executed Nicholas Berg wanted to "shake" America's resolve in bringing democracy to the war-torn country.

The Defense Department is conducting multiple investigations into the abuse, and congressional hearings are under way, as well. At the insistence of lawmakers, the Pentagon arranged for members of Congress to view photos and videos during the day. They depict the abuse, including examples of prisoners forced into sexually humiliating poses.

Durbin noted that one American GI was missing in Iraq, his whereabouts unknown. Given the circumstances, he asked Rumsfeld, "wouldn't it help if there was clarity from you and from this administration that we would abide by the Geneva Convention when it comes to civilian and military detainees unequivocally?"

Expanding his question to include detainees in Afghanistan and Guantanamo Bay, he asked whether such a declaration would "also serve to help American prisoners" held captive.

Rumsfeld replied that the Geneva Convention applies to all prisoners held in Iraq, but not to those held in Guantanamo Bay (search), where detainees captured in the global war on terror are held.

Any Al Qaeda or Taliban personnel taken prisoner are to be treated consistent with the Geneva Convention, under a decision made by Bush, Rumsfeld added.

He said the distinction is that the international rules govern wars between countries but not those involving groups such as Al Qaeda. "Terrorists don't comply with the laws of war. They go around killing innocent civilians," Rumsfeld added.

A second Democrat, Sen. Patrick Leahy of Vermont, said that a report issued in March by Human Rights Watch (search) "corroborated such things" as sleep deprivation, prisoners kept naked in sleeping cells or forced to stand or kneel for hours.

The report covers prisoners held in Afghanistan, he said, adding it "appears to be exactly the same technique" as was employed in Iraq.

Rumsfeld and other Pentagon officials have said the abuses in Abu Ghraib were unauthorized actions taken by a handful of personnel, and Maj. Gen. Antonio Taguba (search), who investigated the mistreatment, testified to that effect before a Senate committee on Tuesday.

Half a world away, there were further repercussions.

Brig. Gen. Mark Kimmitt announced that two more American soldiers have been ordered to stand trial in the Abu Ghraib prisoner abuse scandal although no date for the courts-martial was set. Sgt. Javal Davis, 26, of Maryland and Staff Sgt. Ivan L. "Chip" Frederick II of Buckingham, Va., were ordered to undergo a general court-martial (search), Kimmitt said. Spc. Jeremy C. Sivits, of Hyndman, Pa., goes on trial May 19 before a special court martial, which cannot levy as severe a sentence as a general court-martial.

Taguba told the Senate Armed Services Committee that military police who acted improperly did so "of their own volition." But several senators questioned whether low-ranking soldiers would have created the sexually humiliating scenarios by themselves.

"It implies too much knowledge of what would be particularly humiliating to these Muslim prisoners," said Sen. Susan Collins, R-Maine. "And that is why, even though I do not yet have the evidence, I cannot help but suspect that others were involved, that military intelligence personnel were involved, or people further up the chain of command."

Sen. Ben Nelson, D-Neb., challenged Taguba on his statement that Brig. Gen. Janis Karpinski, who headed the 800th Military Police Brigade at the prison, bore responsibility for a breakdown in discipline that led to abuse.

Taguba testified that orders were issued taking tactical control of the Abu Ghraib facility away from Karpinski and giving it to Col. Thomas M. Pappas, commander of the 205th Military Intelligence Brigade.

"It was clear that he was directed to be the forward operating base commander there for security detainees and force protection," Taguba said. "However, General Karpinski challenged that and she noted that in her recorded testimony."

Taguba said the order placing Pappas in charge of prison policy where Karpinski's MPs worked created a confusing situation and was contrary to Army doctrine. Nonetheless, he found that Karpinski retained overall responsibility for the MPs in her brigade and assigned much of the blame for the abuse to inadequate leadership on her part.

Asked to put in simple words how the abuses happened, Taguba said: "Failure in leadership, sir, from the brigade commander on down. Lack of discipline, no training whatsoever and no supervision. Supervisory omission was rampant."

Karpinski has been suspended and issued an official letter of admonishment in connection with the abuse. She has not been charged and has asserted other officers are attempting to make her a scapegoat.