Ex-Defense Secretary Donald H. Rumsfeld and other top former Pentagon brass denied any cover-up and rejected personal responsibility Wednesday for the military's bungled response to Army Ranger Pat Tillman's friendly-fire death in Afghanistan.

"I know that I would not engage in a cover-up. I know that no one in the White House suggested such a thing to me. I know that the gentlemen sitting next to me are men of enormous integrity and would not participate in something like that," Rumsfeld told a House committee.

It was Rumsfeld's first public appearance on Capitol Hill since President Bush replaced him with Robert Gates late last year. At a hearing he reiterated previous testimony to investigators that he didn't have early knowledge that Tillman was cut down on April 22, 2004, by fellow Rangers, not by enemy militia as was initially claimed.

The truth was kept from the public and Tillman's own family until five weeks later — May 29, 2004. Tillman's mother, Mary Tillman, and other family members watched from the back row at Wednesday's hearing before the House Oversight and Government Reform Committee.

Retired Gen. Richard Myers, former head of the Joint Chiefs of Staff, said he learned of the likelihood of friendly fire toward the end of April but that it wasn't his responsibility to inform the White House or the Tillman family.

"I don't think there's any regulation that would require me to do anything," said Myers.

Rumsfeld and Myers both said they couldn't remember precisely how they learned of Tillman's death or that it might be friendly fire.

Tillman's death received worldwide attention because he had walked away from a huge contract with the National Football League's Arizona Cardinals to enlist in the Army after 9/11.

Committee Chairman Henry Waxman, D-Calif., charged that unanswered questions surrounding Tillman's death reach into the highest ranks of the Pentagon and beyond.

"The concealment of Cpl. Tillman's fratricide caused millions of Americans to question the integrity of our government, yet no one will tell us when and how the White House learned the truth," said Waxman.

But Rumsfeld said he'd always impressed upon Pentagon underlings the importance of telling the truth.

"Early in my tenure as secretary of defense, I wrote a memo for the men and women of the Department of Defense," Rumsfeld said. "You will note that principle number one — the very first — was: 'Do nothing that could raise questions about the credibility of DOD.' "

Rumsfeld gave the committee a copy of that memo.

Before the hearing started, Rumsfeld entered smiling and shook hands with Myers and retired Gen. John P. Abizaid, former commander of the U.S. Central Command.

Both joined him at the witness table.

Two activists held signs reading "war criminal."

"Are you not ashamed?" one said. Rumsfeld didn't react.

The congressional inquiry comes a day after the Army laid most of the blame for the response to Tillman's death on Philip Kensinger, a retired three-star general who led Army special operations forces after the Sept. 11, 2001, attacks.

The Army censured Kensinger for "a failure of leadership" and accused him of lying to investigators probing the aftermath of Tillman's death.

Army Secretary Pete Geren insisted, however, that there was no intentional Pentagon cover-up.

A review panel made up of four-star generals will decide whether Kensinger should have his rank reduced. Geren also announced lesser punishments of seven other officers.

That wasn't good enough for Democrats, who along with Tillman's family suspect a cover-up that goes all the way to the White House.

Rep. Elijah Cummings, D-Md., questioned Rumsfeld's truthfulness when the former secretary said he did not know of the possibility Tillman was killed by friendly fire for about a month after the death.

"It does not seem credible that you didn't know this information," Cummings said.

He then demanded of Rumsfeld, Myers, Abizaid and retired Gen. Bryan Douglas Brown, former commander of the U.S. Special Operations Command: "I ask all of you, do you think there was a cover-up by DOD?"

"Every single (investigation) has suggested that it was badly handled, and errors were made, but in no instance has any evidence of a cover-up, to use the phrase you used, been presented or put forward," Rumsfeld said.

"There was never any attempt to cover up anything. In fact this was not an issue that we discussed," Myers said.

"No, sir, I don't think there was a cover-up, I think people tried to do the right thing and the right thing didn't happen," Abizaid said.

"I don't think there was a cover-up," Brown agreed.

Waxman wanted to hear from Kensinger, and the committee issued a subpoena Monday for his testimony but U.S. marshals weren't able to deliver it.

Kensinger's attorney, Charles W. Gittins, told The Associated Press by e-mail Tuesday night that Kensinger was away on business travel and had declined to "participate in a hearing that is all about show and no substance."

Gittins said his client "had no reason to lie" and had told investigators "everything he knows" about the case. In May, in a rebuttal letter to the general who reviewed the matter, Kensinger firmly rejected all accusations that he had lied.

Among possible evidence of White House knowledge, lawmakers cited a memo written by a top general seven days after Tillman's death warning it was "highly possible" the Army Ranger was killed by his own comrades and making clear his warning should be conveyed to the president.

President Bush made no reference to the way Tillman died in a speech delivered two days after the memo was written.

A White House spokesman has said there's no indication Bush received the warning in the memo written April 29, 2004, by then-Maj. Gen. Stanley McChrystal to Abizaid.

Abizaid said he didn't see the memo until later.

McChrystal was spared punishment in the investigation report released Tuesday.