Officials from the Bush and Clinton administrations testified Tuesday that they did the best they could to protect the American people from terrorist attacks leading up to the Sept. 11, 2001, attacks.

But a bipartisan panel investigating the deadliest act of terrorism in U.S. history said the two White Houses engaged in fruitless diplomatic efforts instead of using secretly planned military actions against Al Qaeda (search) and its leader, Usama bin Laden, prior to Sept. 11.

Those actions, or lack thereof, allowed bin Laden and the terror network leaders to elude capture, said the report from the National Commission on Terrorist Attacks Upon the United States (search).

Top officials testifying before the commission on Tuesday countered that the 19 hijackers would have flown commercial airliners into the Pentagon and World Trade Center even if the United States had been able to kill bin Laden. About 3,000 people died in the attacks.

Such an action might have been a "bold stroke" that "sounded good," Defense Secretary Donald Rumsfeld (search) testified, but the Bush administration was still very new, and was still constructing a comprehensive policy to fight terrorism.

"Rooting out and dealing with terrorist enemies is tough. It will require that we think very differently than we have in the past century," Rumsfeld said, adding that when he took office, President Bush had a "determination to prepare for the new threats of the 21st century."

Rumsfeld: No Going Back

"History shows it can take a tragedy like Sept. 11 to awaken the world to new threats and to take action," Rumsfeld said. "If we're to continue to live as free people we cannot go back to thinking the way the world thought on Sept. 10."

The United States has not yet grasped the danger of the "gathering storm" of terrorism and needs to be prepared for future attacks, former Defense Secretary William Cohen (search) testified earlier.

"I believe that we have been complacent as a society," said Cohen, a Republican who led the Pentagon under former President Clinton. He added that the fact there has been no attacks on U.S. soil since Sept. 11, 2001, "is a dangerous delusion. The enemy is not only coming but he's been here."

The Clinton administration had early indications of terrorist links to bin Laden and Sept. 11 mastermind Khalid Sheikh Mohammed (search) as early as 1995, the report said, while the Bush team may not have listened to terrorist chatter going on in early 2001.

The officials all said that based on intelligence they had at the time, they made the decisions they thought best.

"I knew of no intelligence in the six-plus months leading up to Sept. 11 that indicated terrorists would hijack commercial airliners, use them as missiles to fly them into the pentagon or World Trade Center towers," Rumsfeld said.

The Bush administration was "well aware" of the global threat posed by terrorists when George W. Bush took office in January 2001, Secretary of State Colin Powell (search) testified.

"We were well aware that no nation is immune to terrorism ... we knew that its evil leaders and followers espouse many false causes but have one common purposes - to murder innocent people," Powell said, adding Al Qaeda still "continues to be the No. 1 organization we need to concern ourselves with."

Former Secretary of State Madeleine Albright (search) testified that the Clinton administration actively tried to thwart terrorist actions, and she spent "every single day trying to assess what the terrorist threats were."

Cohen said "we have a solemn responsibility" to the victims of that day to figure out what, if anything, could have been prevented or done differently.

"I think all of us who have held the public trust have to be accountable for what we did and not do during our careers in public service," Cohen said. "Sept. 11 was a life transforming event I think for all of us."

Powell: 'We Wanted to Destroy Al Qaeda'

Powell said the need for "continuity" during the transition period from the Clinton to Bush White House was needed so the terrorists wouldn't take advantage of any loss of focus. He pointed out that staffers from the Clinton administration remained working for Bush, including CIA Director George Tenet (search) and Richard Clarke (search), Clinton's counterterrorism adviser, who stayed on at the National Security Council.

"President Bush and the entire national security team understood that terrorism had to be our highest priority and it was," Powell said. "We wanted to move beyond the roll-back policy of containment, criminal prosecution and limited retaliation for specific terrorist attacks. We wanted to destroy Al Qaeda."

Not until the day before the Sept. 11 attacks did U.S. officials settle on a three-year strategy to overthrow the Taliban Afghan government if a final diplomatic push to get bin Laden failed, the panel's report said.

The Bush White House plan for knocking out terrorism was completed just days before the Sept. 11 attacks. On Sept. 4, Powell said, most of the threats facing the United States at that time were believed to be coming from outside of the country.

One issue the panel is probing is whether the two administrations used military force soon enough and effectively enough.

"I do believe that when we had evidence, we used force," Albright said, pointing to the fact that the United State bombed Baghdad after the 1993 assassination attempt on former President George H.W. Bush, who was in the White House before Clinton.

"We reacted, I think, very strongly … we were prepared to use military force when it was effective," she continued. "We have to put ourselves in pre-9/11 mode …we were most accused of overreacting, not underreacting."

Rumsfeld noted that immediately after Sept. 11, no one questioned going aggressively after the terrorists and those who harbor them, but now the military successes in Afghanistan are taken "largely for granted," as is the U.S. building of a 90-member coalition in the War on Terror.

Albright also said that although the Clinton White House didn't have good intelligence connecting bin Laden with the Taliban, she put the screws to Saddam Hussein.

"I was as hawkish on Saddam Hussein as anybody," Albright said.

Cohen, a former Republican senator from Maine, said just because weapons of mass destruction have not yet been found in Iraq does not mean the search for them is "not just another exercise in the cynical exploitation of fear."

Cohen: 'We Were Trying to Get bin Laden'

Clinton officials were asked why they avoided a military approach despite knowledge that Al Qaeda terrorists had planned attacks to coincide with the Dec. 31, 1999, millennium festivities and after the Cole bombing.

"We were trying to get bin Laden in any event, whether it was before the Cole or after the Cole," Cohen said. "It was the considered judgment at the time that that wouldn't have gotten bin Laden" or helped persuade Pakistan or any other countries to join the United States' hunt.

The 10-member commission invited Bush's national security adviser, Condoleezza Rice (search) to testify, but she declined, citing separation of power concerns involving its staff appearing before a legislative body. Rice met privately with commission members for four hours on Feb. 7.

On Wednesday, Clarke, Tenet and Clinton National Security Adviser Sandy Berger (search) are scheduled to testify.

The Associated Press contributed to this report.