And as ABC News found, much of that recruiting is taking place in Pakistan.
A yearly gathering in a field held this week outside Lahore, Pakistan, is one of the places where U.S. and Pakistani officials say al Qaeda has been able to find new recruits.
THE BLOTTER RECOMMENDS
The gathering is attended by more than a million religious, conservative Muslims who belong to a group that opposes violence.
But intelligence sources tell ABC News that al Qaeda uses the setting as cover.
"It's where they, every year, they send operatives to recruit people, to raise funds and to plot attacks against the West," said Alexis Debat, a Senior Fellow at the Nixon Center and an ABC News consultant.
Pakistani officials say some of the al Qaeda meetings have taken place in a building compound on the grounds where access is closely guarded.
Debat took these pictures as he worked his way into the compound this week.
It was here two years ago in November 2004 that, intelligence sources in Pakistan say, two of the London subway bombers met with al Qaeda commanders.
"This is kind of the heart of this whole terrorist activity on the site; it's this compound," Debat says.
The gathering this week comes against a backdrop of raging anti-American sentiment in Pakistan, particularly following an air strike last month on an Islamic school suspected of training terrorists in northern Pakistan.
Eighty people were killed in the attack, and the former CIA station chief in Pakistan fears al Qaeda will use it to its advantage.
"The risk in Pakistan is always very high, and the recruitment is taking place all the time," says former CIA Director of Counterterrorism Robert Grenier, who is now with Kroll, a security consulting firm. "But after something like this has occurred, I would say the opportunities for recruitment are that much greater."
In fact, tensions are now considered so high in Pakistan that intelligence sources fear it will be difficult for the U.S. to launch any new air strikes inside the country for months to come.