WASHINGTON, May 16 — Leading lawmakers from both parties vowed today to pursue the Iraq prisoner abuse scandal as high as it goes, even as controversy erupted over accusations that top Pentagon officials approved tougher interrogation tactics for Iraq in an urgent effort to gain intelligence to stop surging violence last summer.
The latest controversy surrounded assertions by the journalist Seymour M. Hersh that Defense Secretary Donald H. Rumsfeld had approved a policy decision, pressed by Stephen A. Cambone, the undersecretary of defense for intelligence, to expand a highly secret operation, originally focused on hunting Al Qaeda militants, to include the interrogation of Iraqi prisoners. This operation was reported to have encouraged physical coercion and sexual humiliation of prisoners.
Mr. Hersh has made several revelations in the abuse scandal, but the Defense Department criticized his new article in The New Yorker in the very toughest of terms. It said assertions in his article were “outlandish, conspiratorial and filled with error and anonymous conjecture.”
His accusations nonetheless were the focus of wide debate among senators and others interviewed on Sunday talk shows, who promised the Senate would investigate fully.
These developments came as the Bush administration moved further to redress problems in Iraq detention centers while struggling to overcome the spreading scandal, an apparent factor in the recent decline of President Bush’s approval ratings to their lowest point yet.
The senior army general in Iraq, Lt. Gen. Ricardo Sanchez, moved late last week to eliminate the most coercive interrogation tactics at Abu Ghraib prison and other detention centers. He told military intelligence chiefs that case-by-case requests for unusually harsh techniques would no longer be approved.
Over the weekend, the focus grew on how high up the chain of command the orders permitting abuse originated, and whether top Pentagon officials either authorized excessive tactics or contributed to an atmosphere of laxity in interpreting and respecting prisoner-treatment standards.
Like Mr. Cambone, senior military officials have insisted that all those interrogation techniques approved for use have been allowable under international law. Mr. Cambone said they were included in the Army manual and followed the Geneva Conventions.
And the Pentagon statement denouncing Mr. Hersh’s article said that the abuse at Abu Ghraib depicted in hundreds of photos and videotapes “has no basis in any sanctioned program, training manual, instruction or order in the Department of Defense.”
The scandal has met with universal outrage in Washington but mixed views on how high responsibility can be traced.
The president and other administration officials have referred repeatedly to the “few” responsible for abuses.
But many in Congress have said that only by following the chain of command aggressively, and punishing those responsible to the fullest extent proper, can the air be cleared and the severe damage to the United States’ image begin to be fixed.
“We need to take this as high up as it goes,” said Senator John McCain, Republican of Arizona, “and we need to do it quickly.”
“You’ve got to get everything out as quickly as possible, take remedial action,” Mr. McCain said on the NBC News program “Meet the Press.”
A senior Democrat who has been supportive of the Iraq war, Senator Joseph I. Lieberman of Connecticut, agreed.
“The search for truth should take us wherever it leads,” he said on CNN. “That’s the only way we’re going to restore the honor of the United States.”
Senator Carl Levin of Michigan, the ranking Democrat on the Senate Armed Services Committee, said the abuse was part of “a process, not just the spontaneous actions of a few M.P.’s,” or military police guards.
Mr. Rumsfeld has survived early calls for his resignation. Mr. Bush issued a verbal rebuke to the defense secretary, but followed it with praise a few days later for a “superb” job. Mr. Rumsfeld would likely still be vulnerable if he were connected to orders that led to abuse.
The Army general who led the central investigation of abuses at Abu Ghraib, Maj. Gen. Antonio M. Taguba, told the Senate last week that “we did not find any evidence of a policy or a direct order given to these soldiers to conduct what they did.” He added, “I believe that they did it on their own volition.”
Some of the soldiers facing military trial for the abusive practices have blamed incitement or encouragement from their officers. But another, Army Specialist Jeremy C. Sivits, said their officers would have “slammed” them had the practices been known.
But Mr. Hersh writes that amid high frustration last summer over a series of bloody setbacks in Iraq, including the deadly August bombings of the Jordanian Embassy and of United Nations headquarters in Baghdad, Mr. Rumsfeld and Mr. Cambone sought urgently to increase the productive intelligence obtained from Iraqi prisoners.
According to the article, Mr. Rumsfeld approved a decision from Mr. Cambone — the top Pentagon official for intelligence — to give a highly secret operation a role in prisoner interrogation. With their approval, Mr. Hersh writes, “male prisoners could be treated roughly, and exposed to sexual humiliation.”
Mr. Hersh quotes a former intelligence official as saying that this produced significant new intelligence, which in turn led to more arrests and detentions and fuller prisons.
“The goal was to use a couple of very harsh means — one, sexual humiliation, another, a more physical force,” Mr. Hersh said on the CBS News program “Face the Nation.”
“That — and I’m not saying Rumsfeld authorized what we saw in the last few weeks, but he did authorize these guys to come into the prison system and jack it up, get better stuff,” he said.
Secretary of State Colin L. Powell said today that the abuse scandal had been “damaging” to the United States’ image, but he denied any knowledge of the Hersh accusations.
“It has been damaging, there is no doubt about it,” he said.
But he added, “The United States is a moral nation. And the world will now see how we bring people to justice for their misbehavior.”
He suggested that he would like to see the same sort of outrage in the Arab world over the decapitation of a civilian American in Iraq, Nicholas Berg, as over the prison abuse.
“To have him murdered on camera, so that his parents could see it, with his throat being slit by one of the worst terrorists on the face of the Earth,” Mr. Powell said, was “equal to any other act you’ve seen with respect to the need to condemn it.”