ISIS, the Islamist terror group that now controls much of Syria and Iraq, poses an "extremely high" terror threat to U.S. targets, and has the bomb-making skills and foreign fighters needed to strike U.S. and other Western interests, according to multiple U.S. intelligence officials.
"While trying to rank threats or compare them to previous threat periods is a hazardous endeavor," said one former U.S. counterterrorism official, "the current threat coming out of ISIS -- and Syria more broadly -- is extremely high." While the opposition in Syria and Iraq is diverse, said the official, there are "sub elements" within it that are "especially worrisome because of their commitment to attack the West."
Another senior counterterrorism official added that in recent weeks, "ISIS has accumulated tens of millions in wealth, large amounts of military equipment and ordnance, and has expanded the safe haven in which it operates." During this same period, the number of potential U.S. targets in the region -- meaning U.S. military personnel -- has increased.
Both officials noted, however, that ISIS leader Abu Bakr al-Baghdadi is currently preoccupied with building an Islamic state across a broad swath of Iraq and Syria, not attacking the U.S. at home or abroad. "It's not his focus right now," said the second official, even though "al-Baghdadi's rhetoric alone would suggest that he does have … international ambitions."
And Rep. Peter King, R.-New York, who sits on the House Committee on Homeland Security, said there was no known "immediate threat" to the U.S. homeland from ISIS, though the global terror threat is mounting as more and more groups like ISIS pop up in Africa and the Middle East.
U.S. officials tell NBC News that about 70 Americans have traveled to Syria to fight alongside opponents of the Assad regime and about a dozen are currently active. Some have returned to the U.S.
The FBI tells NBC News that it is investigating "a handful" of individuals who have traveled to Syria from the Minneapolis region.
British officials say their concern about domestic terrorism from ISIS and other foreign fighters in Syria is higher due to the larger number of British residents who have traveled back and forth to Syria. They estimate 400 to 500 British "foreign fighters," including Muslim converts, have gone to Syria, and about two thirds have come back to the U.K.
"The threat picture here is even greater than the U.S. and it creates a situation that is difficult, complex and of great concern," said one British official. The official noted that the threat needed to be viewed as one that impacted all of Europe.
If ISIS were to attack Western targets, the job is made easier by access to the huge quantity of military supplies now available in Iraq and Syria, and access to the kind of potential attackers - passport holders in Western countries -- who can move unnoticed in the U.S. and Europe.
Said one expert, "The number of potential attackers is significantly greater than we have seen from any other safe haven since 9/11."
ISIS has also not been degraded by the kind of military action, including drone strikes, that has killed militants in Afghanistan, Yemen and Somalia.
"The lack of U.S-led disruptive activity means that elements in Syria and Iraq have greater freedom to plot than in any other safe haven," said the expert.