"Al Qaeda remains the pre-eminent threat against the United States," Mike McConnell told a Senate hearing more than six years after the September 11, 2001, attacks.

Mr. McConnell said that fewer than 100 Al Qaeda terrorists have moved from Iraq to establish cells in other countries as the American military clamps down on their activities, and the organization "may deploy resources to mount attacks outside the country."

Mr. McConnell said while the level of violence in Iraq has dropped sharply since last year, it is going to be years before Iraq is stable.

"It is not going to be over in a year. It's going to be a long time to bring it to closure," he said.

The Al Qaeda network in Iraq, Pakistan, and Afghanistan has suffered setbacks, but he said the group poses a persistent and growing danger.