Defense Secretary Donald H. Rumsfeld (search) warned members of Congress (search) that the Iraq prison abuse scandal could worsen with the release of videos and more photographs depicting brutality.

With his future in the Cabinet possibly in jeopardy, Rumsfeld apologized and told House and Senate committees Friday that he took full responsibility for the abuses at the Abu Ghraib (search) prison. Rumsfeld offered "my deepest apology" to Iraqis abused by American soldiers and said he would seek compensation for them. He also said those responsible would be punished.

But it's not clear whether the hearings, broadcast live nationwide, would ease pressure on Rumsfeld to resign. Lawmakers said they were pleased by his apology, but some said his testimony left questions unanswered about who was giving orders and why Congress wasn't told earlier about the extent of the abuse.

Rumsfeld said he wouldn't resign "simply because people try to make a political issue out of it," but he didn't rule out the possibility of stepping down. He said if he could not be effective, "I certainly wouldn't want to serve. And I have to wrestle with that."

Asked by Sen. Evan Bayh (search), D-Ind., if he would step down if that would help undo the some of the damage caused by the scandal, Rumsfeld said "that's possible."

President Bush reiterated his support for Rumsfeld, telling reporters on his campaign bus after traveling through western Wisconsin on Friday the secretary is a "great" Cabinet member.

"He'll remain in my Cabinet, period," the president said.

The photographs of stripped, hooded Iraqi prison inmates being sexually humiliated by their American captors has caused outrage throughout the world, aggravating anti-American sentiment throughout the Middle East and severely undermining American credibility in Iraq.

Rumsfeld said there are many more photographs and videos that have not been made public yet.

"It's going to get still more terrible, I'm afraid," he said.

Sen. Lindsey Graham, R-S.C., said he wants to "prepare the public: Apparently the worst is yet to come potentially in terms of disturbing events."

He later told reporters, "The American public needs to understand we're talking about rape and murder here. We're not just talking about giving people a humiliating experience."

He did not elaborate, but a Senate aide, speaking on condition of anonymity, said senators have been told videotapes are believed to exist showing rape and the corpses of what are possibly murder victims. The tapes were described in an additional part of an investigative report. The Pentagon has not yet submitted that additional part of the report to senators, the aide said.

In his appearances, Rumsfeld offered Congress a rare display of public contrition, while continuing to defend the military's actions and questioning of his critics' political motivations.

His apology came one day after Bush offered his own regrets. Rumsfeld said the treatment of prisoners was "inconsistent with the values of our nation. It was inconsistent with the teachings of the military ... and it was certainly fundamentally un-American."

During a total of six hours of testimony, Rumsfeld sought to repair the damage done to American prestige aboard, to ease the anger of lawmakers caught off guard by the uproar and to shore up support for his own job.

He said bluntly, "These events occurred on my watch. As secretary of defense, I am accountable for them."

His testimony won praise from Senate Majority Leader Bill Frist and Senate Armed Services Committee Chairman John Warner, R-Va.

Others lawmakers were more guarded. Sen. John McCain, R-Ariz., said "I think the secretary did an effective job. I believe that there is a lot more that needs to be discussed and a lot more answers that need to be given." Another Republican, Sen. Susan Collins of Maine, also said "I still think there are many unanswered questions."

During the Senate hearing, the panel's top Democrat, Sen. Carl Levin, D-Mich., noted with "deep dismay" that Rumsfeld and Gen. Richard Myers, the chairman of the Joint Chiefs of Staff, had briefed lawmakers about Iraq in a classified session last week but did not mention the major story they knew was about to break on CBS.

But after the hearing, Levin wasn't ready to call for Rumsfeld's resignation.

"If I thought his resignation would change the policies of this administration relative to Iraq, I'd be all for it," he said.

Rumsfeld repeatedly told members of Congress he and Bush were "blindsided" by the photos when they were broadcast. He said the pictures had been leaked, and had not yet reached the Pentagon when they appeared on television.

He also said that Army officials had publicly disclosed the abuse when it was first reported and announced investigations into it. He said Pentagon officials did not press for details because they did not want to interfere with the investigation.

Rumsfeld said a panel of retired officials would report within 45 days on "the pace, the breadth, the thoroughness of the existing investigations" and determine whether more inquiries were needed.

After the hearing, he said the board was expected to include former Rep. Tillie Fowler of Florida, who has headed the Air Force Academy's oversight board into sexual assaults; James Schlesinger, a defense secretary from 1973 to 1975; and retired Air Force Gen. Chuck Horner. One other person is yet to be named.