The memo, from former counterterrorism chief Richard Clarke to then-national security adviser Condoleezza Rice, had been described during the hearings but its full contents had not been disclosed.

Clarke, a holdover from the Clinton administration, had requested an immediate meeting of top national security officials as soon as possible after Bush took office to discuss combating al Qaeda. He described the network as a threat with broad reach.

"Al Qaeda affects centrally our policies on Pakistan, Afghanistan, Central Asia, North Africa and the GCC (Gulf Arab states). Leaders in Jordan and Saudi Arabia see al Qaeda as a direct threat to them," Clarke wrote.

"The strength of the network of organizations limits the scope of support friendly Arab regimes can give to a range of U.S. policies, including Iraq policy and the (Israeli-Palestinian) Peace Process. We would make a major error if we underestimated the challenge al Qaeda poses."

The memo also warned of overestimating the stability of moderate regional allies threatened by al Qaeda.

It recommended that the new administration urgently discuss the al Qaeda network, including the magnitude of the threat it posed and strategy for dealing with it.

The document was declassified on April 7, 2004, one day before Rice's testimony before the Sept. 11 commission. It was released recently by the National Security Council to the National Security Archive -- a private library of declassified U.S. documents obtained through the Freedom of Information Act.

The meeting on al Qaeda requested by Clarke did not take place until Sept. 4, 2001.