Speaking Friday to reporters at Washington headquarters of FBI (Federal Bureau of Investigation, James Comey emphasized that he was "determined" to keep any scenario similar to the September 11, 2001 attacks arising out of Syria, as more foreign fighters join the insurgency, which Washington and its European and Middle East allies have backed.

Comey compared the war in Syria to Afghanistan in the 1980s and 90s, when US-sponsored foreign and Afghan fighters there eventually formed al-Qaeda and declared war on the United States, allegedly leading to 9/11 attacks in New York and Washington, using passenger planes as weapons.

The FBI director, however, assessed that Syria insurgents would be considerably more dangerous that those that fought the Russian military invasion of Afghanistan in the 80's.

"All of us with a memory of the 80s and 90s saw the line drawn from Afghanistan in the 80s and 90s to September 11. We see Syria as that but an order of magnitude worse," Comey said.

The FBI chief further said the number of Americans who had either travelled to Syria or sought to do so had grown by a few dozen since the start of the year and that there were Americans among the foreign-backed insurgents in Syria that were trying to recruit others from the US.

The problem was "getting worse, just because with time more and more people are traveling there from here (the US) and all over the world" to take part in the Syria fighting, he said.

Comey predicted "there's going to be a diaspora out of Syria at some point", adding that he was "determined not to let lines be drawn from Syria today to a future September 11".

US law enforcement officials have expressed concern about the influence of extremist insurgents in Syria, many of them linked to al-Qaeda, as they seek to foment the unrest in the war-torn country.

Officials say fighters from the US or Europe looking to join the cause could easily become radicalized and impart those beliefs on their return home.

NTJ/MB