Former top counterterrorism adviser Richard A. Clarke told a special commission today that the Bush administration initially did not treat terrorism as "an urgent issue" and sidetracked his proposals to deal with the threat more aggressively.

Clarke, appearing before the bipartisan commission investigating the Sept. 11, 2001, terrorist attacks, also criticized the FBI's performance in assessing domestic threats from the al Qaeda terrorist network before the attacks and called for the creation of a new domestic intelligence agency.

The testimony by Clarke, who has served in the past four administrations, came amid a political firestorm over the publication this week of a book in which he described the Bush administration as relatively lax in its approach to terrorism before Sept. 11 and obsessed with trying to blame Iraq afterward.

Clarke, who headed the National Security Council's Counterterrorism Security Group under Presidents Bush and Clinton, apologized in his opening statement to relatives of the Sept. 11 victims, some of whom attended the hearing.

"Your government failed you, those entrusted with protecting you failed you, and I failed you," Clarke said. "For that failure, I would ask . . . for your understanding and forgiveness."

Clarke said that in the Clinton administration, there was no higher priority that fighting terrorism in general and al Qaeda in particular. But he said that "the Bush administration in the first eight months considered terrorism an important issue, but not an urgent issue." He and CIA Director George J. Tenet "tried very hard to create a sense of urgency," Clarke said. "Although I continued to say it was an urgent problem, I don't think it was ever treated that way."

In a morning session, the commission was told of confusion within the nation's intelligence community during both the Clinton and Bush administrations about whether the CIA had the authority to kill al Qaeda leader Osama bin Laden.

But even if he had been killed, that would not have prevented the Sept. 11 attacks, Tenet testified.

"I believe that this plot line was off and running," he told the 10-member panel investigating the attacks on the World Trade Center and the Pentagon. "Operators were moving into this country. . . . This plot was well on its way," he said.

"Decapitating one person -- even bin Laden in this context -- I do not believe we would have stopped this plot."

Under questioning by Republican members of the commission, Clarke, who said he voted Republican in 2000, rebutted charges by the White House that he was engaged in a partisan political attack. He also dismissed reports that he was seeking a high-level post in a future Democratic administration should Sen. John F. Kerry of Massachusetts win the November election against President Bush.

"I will not accept any position in a Kerry administration, should there be one," Clarke said, stressing that he was speaking "on the record, under oath."

Asked about his book's strong criticism of the Bush administration compared to a greater focus on shortcomings of the Clinton administration during his 15 hours of previous testimony to the Sept. 11 commission in closed session, Clarke noted that no one on the panel had asked him his opinion of the U.S. invasion of Iraq.

"By invading Iraq . . . the president of the United States has greatly undermined the war on terrorism," Clarke told the commission today.

Clarke said he had urged National Security Adviser Condoleezza Rice in a memo on Jan. 25, 2001 -- a few days after President Bush's inauguration -- to hold an urgent high-level meeting to review proposals to deal with al Qaeda. In response, Clarke said, he was told that he should report to a committee of deputies, and not the "principals," such as Rice and Cabinet-level officials, on his package of recommendations.

That decision "slowed it down enormously," as did a decision to consider the proposals only "as part of a cluster of policy issues" that also included such matters as nuclear proliferation in South Asia and democratization in Pakistan, Clarke said.

Clarke said he became so frustrated that he asked to be assigned to a new position dealing with cyber security.

"My view was that this administration, while it listened to me, either didn't believe me that there was an urgent problem, or was unprepared to act as though there was an urgent problem," Clarke said.

He said he wrote a memo to Rice on Sept. 4, 2001, that criticized the Defense Department for reluctance to use force against al Qaeda and the CIA for impeding the deployment of unmanned Predator drones to hunt for bin Laden. The memo urged officials to imagine a day when hundreds of Americans lay dead from a terrorist attack and ask themselves what more they could have done.

His proposals were eventually implemented, Clarke said, but only after Sept. 11. "I didn't really understand why they couldn't have been done in February" 2001, he said.

He said that with a more robust intelligence and covert action program in the years before the attacks, "we might have been able to nip [the plot] in the bud." But the gathering and sharing of intelligence was so poor that it hardly mattered that there was no specific information pointing to an attack in the United States before Sept. 11 and that attention was focused overseas, he said.

"I hate to say it [but] I didn't think the FBI would know whether there was anything going on in the United States by al Qaeda," Clarke said. He said neither he nor senior FBI officials were provided with information that two known al Qaeda members, who eventually participated in the attacks, had entered the United States.

Rice has refused to testify in open session before the commission, citing the separation of powers between the legislative and executive branches. Instead, the Bush administration sent Deputy Secretary of State Richard L. Armitage to defend the administration's actions.

But Armitage stressed that "I'm not here as Dr. Rice's replacement," citing his own expertise on national security matters. He said there had been "stunning continuity" between the Bush administration's initial approach to al Qaeda and the policies of the Clinton administration and that the new government "vigorously pursued" policies inherited from Clinton while developing its own response to al Qaeda.

Echoing remarks he had made in interviews with the commission staff, Armitage said the Bush administration's early policy toward al Qaeda was headed in the right direction, although he conceded that deliberations were slow.

"We were on the right track. We weren't going fast enough," he said.

Earlier, Tenet told the commission that intelligence officials appreciated the danger of al Qaeda and had a growing sense of urgency in the summer of 2001 about an impending disaster, but they thought it would come overseas, not in the United States.

That, rather than the failure to kill bin Laden, was the more serious "systemic" failure.

The testimony today followed the presentation of a report by the committee staff that described a rising sense of frustration in the U.S. intelligence community about the seeming inability of policy makers to decide on, and execute, decisive action to disrupt bin Laden's al Qaeda operation.

Attempts to find, capture or kill bin Laden were undertaken after 1998 under intelligence directives signed by then-President Clinton and continued after President Bush took office in 2001, Tenet told the commission.

The report by the committee staff said there was some disagreement during the Clinton period as to whether the CIA had authority to kill the al Qaeda network leader.

While the Clinton officials told the commission that the president wanted bin Laden dead, "every CIA official interviewed on this topic by the commission," including Tenet, emphasized capturing bin Laden and the only "acceptable context for killing bin Laden was a credible capture operation."

One former chief of the agency's bin Laden unit told the commission, "We always talked about how much easier it would have been to kill him."

But Samuel R. "Sandy" Berger, who served as Bill Clinton's national security adviser, dismissed those concerns and told the commission today that the CIA had the authorization to kill bin Laden.

"If there was any confusion down the ranks, it was never communicated to me nor to the president, and if any additional authority had been requested I am convinced it would have been given immediately," Berger said.

The commission's report found, however, that confusion continued as the summer of 2001 approached, to the point that two veteran counterterrorism agents "were so worried about an impending disaster" that they considered resigning and "going public with their concerns."

The disaster they expected was overseas, not domestic, however, Tenet testified.

"The predominant focus and thread of the reporting took us overseas," he said. While the agency did not "discount the possibly of an attack on the homeland," he said, "the data just didn't exist with any specificity to take you there. I mean, that was what was maddening about this."

The government just did not have the "kind of specificity we needed . . . that would have led us to conclude that the plot was inside the United States. . . . We didn't steal the secret that told us what the plot was. We didn't recruit the right people or technically collect the data, notwithstanding enormous effort to do so."

He said the problem in part was operational and in part systemic.

"We didn't integrate all the data we had properly, and probably we had a lot of data that we didn't know about that, if everybody had known about, maybe we would have had a chance," Tenet said.

He also pointed to the "wall that was in place between the criminal side and the intelligence side" of law enforcement domestically and internationally as an impediment. "Even people in the Criminal Division and the Intelligence Divisions of the FBI couldn't talk to each other, let alone talk to us or us talk to them," Tenet explained.

He said the Patriot Act, passed after 9/11, was "absolutely essential" to breaking down those walls.

"The country was not systemically protected because even in racing through all these threats, sometimes exhaustively -- we exhausted ourselves -- there was not a system in place to say, 'You've got to go back and do this and this and this.'

"It's not criticizing anybody. But the moral of the story is, if you take in those measures systemically over the course of time and closed seams, you might have had a better chance of succeeding stopping, deterring or disrupting."

While there has been extended criticism of the CIA in the past for failing to prevent or provide warning of the 9/11 attacks, Tenet today was repeatedly praised for having pushed the growing danger from terrorism and al Qaeda in the years and even months before they took place.

In July 2001, amid reports the al Qaeda was planning something dramatic, Tenet said the CIA worked with a network of foreign intelligence services to arrest and detain suspected terrorists in Bahrain, Yemen and Turkey. "We cited plots in the Arabian Peninsula and Europe," Tenet told the panel, "and ultimately in August 2001 we warned about bin Laden's desire to conduct terrorist attacks on the U.S. homeland."

Jamie Gorelick, deputy attorney general in the Clinton administration, asked about the lack of coordination among senior Bush administration officials about the threat. She drew a comparison with the Clinton senior-level meetings that took place almost daily in late 1999 to prepare for terrorist threats surrounding the millennium celebrations.

Gorelick said that the commission had been told that Bush's secretary of transportation did not know about the threats and senior officials did not know what data the FBI had in its files.

Tenet said the Bush administration had a different manner of communication in the pre-9/11 period when dealing with terrorism. Under Bush he was talking to the president, the vice present and national security adviser every day, he said.

Tenet said it took a "galvanizing force" to mobilize both the administration and the American public to take the steps needed to meet the terrorist threat.

He noted that even today the agency is still five years away from having the human intelligence capabilities to have access to the sanctuary areas where terrorist groups operate. He also said the commission had to establish benchmarks for the future, saying he worried that other attacks will be coming while memories of the 9/11 attack fade.