Former FBI Director Robert Mueller warned that the current violence in Gaza will inflame anti-U.S. sentiment in the region and exacerbate an increasingly dangerous terror threat to the U.S.

"We cannot forget that what's happening in Gaza today will feed and fuel the desire for many more to join radical groups," Mueller said, speaking at the Aspen Security Forum on Friday. "And with the territory you have in Syria and Iraq, with the difficulties of covering that particular area, I think you may well see as a result of what's happening between Israel and Hamas in Gaza an increase in the months ahead of those that are willing to go and join such groups."

The comments came as U.S. counterterrorism officials express new alarms about a mounting flow of foreign fighters — many with western and U.S. passports—to join militant groups in Syria and Iraq.

Speaking on the same panel as Mueller, National Counterterrorism Center Director Matt Olsen said U.S. officials have uncovered evidence that “veteran” al-Qaida operatives from Pakistan are now in Syria seeking to recruit fighters for possible attacks on the U.S. homeland.

"We certainly see that al-Qaida has identified Syria as the place to go," Olsen said. "[Ayman] al-Zawahri very publicly said that Syria is the place for fighters to go, particularly foreign fighters. ... In addition to the foreign fighter flow to Syria, what is also of concern is that there are a number of veteran al-Qaida individuals now in Syria taking advantage of the really permissive environment that exists there," he said.

U.S. officials have expressed repeated concern in recent months that these foreign fighters may return to their home countries to launch attacks against U.S. and western interests. But Olsen’s comments today gave the first indication that core al-Qaida operatives are seeking to exploit the situation, working to identify and possibly train fighters for terror attacks.

Olsen said U.S. officials are seeking to track the Amercans traveling to Syria — in many cases identifying who they are and which communities they are coming from. But once they arrive in Syria, keeping track of them is more difficult. The influx now "spreads from South Asia, where it was centered several years ago, to large swaths of geography in the Middle East across North Africa. I think right now that the threat is possibly greater and certainly more complex than it's been in recent years,” said Olsen.

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Mueller's comments came during a wide-ranging discussion in which he vigorously defended the use of undercover FBI sting operations to target suspected radical Muslims in the United States.

"If we had an opportunity to do a sting on the brothers in Boston, I would have done that in a heartbeat,” said Mueller, making one of his first public appearances since stepping down as FBI director in September.

Mueller was responding to questions about a Human Rights Watch report this week that sharply criticized the FBI for “overstepping its role” by effectively creating terror plots through the use of undercover informants — a practice that has alienated some Muslim communities in the U.S. "We do not troll in mosques," Mueller said, though entrapment issues are often a risk in prosecuting terrorism cases.



In one such case, the so-called Newburgh Four were convicted of plotting to attack a Jewish community center and a U.S. military base after they were recruited by an undercover FBI informant who offered the defendants up to $250,000 to participate in the plot.





In that case, the subject of an HBO documentary that aired this week, the presiding federal judge, Colleen McMahon, had said at sentencing: “I believe beyond a shadow of a doubt that there would have been no crime here except the government instigated it, planned and brought it to fruition.”

“Was there a conviction?” Mueller shot back when asked about the case.

Mueller also warned that the current crisis over Russian actions in Ukraine is likely to hamper U.S. efforts to crack down on cyberhackers — a large number of whom are believed to be based in that region. Asked how much cooperation the FBI can expect from the Russian FSB in identifying cyberhackers — such as those that attacked Target last year and stole 40 million credit and debit cards — he replied, “Not much.”

Watch the entire panel discussion: