The Bush administration's former top counterintelligence official warned one week before the September 11th attacks that hundreds of Americans could die in a terrorist strike, but said the president did not consider terrorism an urgent issue.
Mr Richard Clarke, who served four US presidents, told the national commission investigating the 2001 attacks on the World Trade Center and the Pentagon: "I believe the Bush administration in the first eight months considered terrorism an important issue, but not an urgent issue."
On the second of two dramatic days of open testimony, one of the most charged moments came when commissioner Mr Tim Roemer, a former Democratic congressman, asked Mr Clarke about a letter he wrote to President Bush's national security adviser, Ms Condoleezza Rice, one week before the attacks.
"You urge policymakers to imagine a day after hundreds of Americans lay dead at home and abroad after a terrorist attack and ask themselves what else they could have done. You write this on September
4th, seven days before September 11th" Mr Clarke simply replied, "Yes."
Mr Clarke, who has given 15 hours of testimony to the commission in closed session, was making his first public appearance. The former official, who served three Republican and one Democratic administrations, created a stir this week by publishing a book accusing the Bush administration of failing to recognize the urgency of the threat posed by bin Laden's al Qaeda network.
In his letter to Ms Rice, Mr Clarke lambasted the Pentagon and the CIA for failing to act against al Qaeda.
The commission is due to report in late July at the height of the presidential campaign.