WASHINGTON — CIA director George Tenet admitted Wednesday that the nation's intelligence agencies failed to recognize the rising threat posed by al-Qaida before the Sept. 11, 2001, attacks and predicted it would take the United States five years to have the kind of clandestine service the country needs.

Tenet and FBI Director Robert Mueller testified before the commission following the release of a sharply critical report of the nation's intelligence community for missteps in preventing the attacks on New York and Washington.

"We all understood bin Laden's attempt to strike the homeland, but we never translated this knowledge into an effective defense of the country," Tenet said. "In the end, one thing is clear: No matter how hard we worked — or how desperately we tried — it was not enough."

Tenet said part of the problem was that the intelligence community was operating throughout the 1990s with a "significant erosion in resources and people and was unable to keep pace with technological change."

But some commissioners expressed frustration at Tenet's suggestion that it would take five years to bring the intelligence community up to speed.

"This is not a new problem," said Vice Chairman Lee Hamilton, a former Democratic congressman from Indiana and member of the House Intelligence Committee. "We've been talking about the difficulty of developing human intelligence for 10 or 15 years."

Both Tenet and Mueller told the commission that they are taking steps to dramatically overhaul the way their agencies collect and analyze intelligence.

The daylong hearing probed what needs to be done to plug intelligence gaps outlined in a highly critical report by the commission's staff. The report, which built off the work of the 2002 joint House and Senate intelligence committee investigation, revealed a broken intelligence apparatus.

"That report that you heard this morning was a damning report," said commissioner John F. Lehman, former secretary of the Navy during questioning of Tenet. "Not of your actions or the actions of any of the really superb and dedicated people that you have, but it was a damning evaluation of a system that is broken, that doesn't function."

Tenet said the intelligence community has devoted itself to "transforming" its collection, operational and analytical capabilities since the Sept. 11 attacks.