ASHINGTON (CNN) -- The head of the Central Intelligence Agency told the panel investigating the September 11, 2001, attacks that the United States was "in effect, unprotected" on that day -- and that the country needs five years to mount the clandestine service it needs.

Committee Chairman Thomas Kean said "I wonder if we have five years ... that worries me a little bit."

"The bottom line is, to do this right, to build the platforms and access and cover and technology that we need, it's budgeted for, the president has recognized it," George Tenet said.

"It's going to take another five years to build a clandestine service the way the human intelligence capability of this country needs to be run."

Tenet told the panel that intelligence officials understood and were taking steps to counter the threat posed by Osama bin Laden's terrorist network, but he acknowledged that mistakes were made. (Watch CNN for live coverage of the hearing and look for the link on the CNN.com main page for a live video stream.)

"Most profoundly, we lacked a government-wide capability to integrate foreign and domestic knowledge, data, operations and analysis. Warning is not good enough without the structure to put it into action," Tenet said.

Tenet said that intelligence officials were not able to turn their knowledge of the threat into an "effective defense of the country."

"Doing so would have complicated the terrorist calculation of the difficulties in succeeding in a vast open society, that in effect, was unprotected on September 11th," Tenet said.

Tenet said that the United States needs another five years "to have the kind of clandestine service our country needs" to beat terrorism.

FBI Director Robert Mueller is scheduled to testify in the afternoon session.

The panel will also hear testimony from John O. Brennan, the director of Terrorist Threat Integration Center; Lt. Gen. Patrick M. Hughes from the Department of Homeland Security; and John S. Pistole and James L. Pavitt, counter terrorism officials from the FBI and CIA, respectively.

A staff report issued at the start of the hearing Wednesday found that the intelligence community was "struggling to collect on and analyze" international terrorism during the mid- to late-1990s.

"While many dedicated officers worked day and night for years to piece together the growing body of evidence on al Qaeda and to understand the threats, in the end it was not enough to gain the advantage before the 9/11 attacks," the report said.

The report said that there were many reports on Osama bin Laden and al Qaeda, but there "was no comprehensive estimate of the enemy."

It also said that intelligence agencies did not conduct a review of what they knew and what they did not know -- so they could answer those questions.

FBI, CIA criticized in hearing
On Tuesday, Attorney General John Ashcroft defended himself against accusations that he showed little interest in terrorist threats before the attacks, and he blamed the Clinton administration for hobbling antiterrorism efforts.

The FBI came in for tough criticism from the commission investigating the attacks, faulted in a staff report for not piecing together "connections" about terrorist activity. (Gallery: Quotes from the testimony)

Ashcroft appeared to criticize the Clinton administration early on in his testimony.

"We did not know an attack was coming because for nearly a decade our government had blinded itself to its enemies," he said. "Our agents were isolated by government-imposed walls, handcuffed by government-imposed restrictions and starved for basic information technology."

Ashcroft criticized his predecessors at the Justice Department, saying a 1995 memorandum by then-Deputy Attorney General Jamie Gorelick -- now a member of the commission -- hamstrung the FBI beyond what the law required.

But former acting FBI Director Thomas Pickard said Ashcroft dismissed warnings of terrorist threats that summer and rejected appeals for additional counterterrorism funds.

Pickard said that "in late June and through July, he met with Attorney General Ashcroft once a week," the report says. "He told us that though he initially briefed the attorney general regarding these threats, after two such briefings the attorney general told him he did not want to hear this information anymore."

Ashcroft disputed Pickard's account when he appeared before the commission, saying he met with him on more than two occasions.

"Secondly, I did never speak to him saying that I did not want to hear about terrorism," Ashcroft said.

Former FBI Director Louis Freeh said the agency's request for more agents and analysts were not fulfilled before 9/11 and he said the country was not on a "war footing" before the attacks.

"We were using grand jury subpoenas and arrest warrants to fight an enemy that was using suicide boats to attack our warships," he said, referring to the attack on the Cole. The fight against terrorism at that time, he said, was not "a real war."

The commission also heard from J. Cofer Black, former head of the CIA's counterterrorism center, who said that intelligence reports in the summer of 2001 indicated a "massive" terrorist strike was in the works.

"None of this, unfortunately, specified method, time or place. Where we had clues, it looked like planning was under way for an attack in the Middle East or Europe," he said.

Black said he and his colleagues at the time "are profoundly sorry. We did all we could. We did our best." But he said the agency faced a shortage of money and staff that "seriously hurt our operations and analysis."

Pickard testified that restrictions within the bureau on sharing intelligence with criminal investigators "hampered greatly" efforts to penetrate al Qaeda cells. He said the hijackers were picked because their background would raise no red flags among U.S. law enforcement.


Former FBI Director Louis Freeh is sworn in for testimony before the 9/11 panel.
The commission reported Tuesday that an effort to locate eventual 9/11 hijackers Nawaf Alhazmi and Khalid Almihdhar in late August 2001 failed, hampered by disputes over how widely agents could share information and a failure of coordination.

Both men -- who flew American Airlines Flight 77 into the Pentagon -- had been identified as attendees at a meeting of terrorist suspects in Malaysia. They could have been held on immigration charges or as material witnesses in the 2000 bombing of the destroyer USS Cole, the report found.

Earlier, Ashcroft's predecessor, Janet Reno, testified that she called on the FBI to improve its ability to share information, both internally and with other agencies. She said she did not know of any legal reason the FBI could not share with other agencies information it had about Almihdhar and Alhazmi.

Reno told the commission that she felt a "certain amount of frustration" in early 2000 in trying to improve the FBI's information-sharing capabilities.