CIA Director John Brennan says the extremist Islamic State (IS) group is attempting to deploy fighters in the West to carry out further attacks, drawing from a pool of tens of thousands of militants throughout the world that outnumbers that of Al-Qaeda at the height of its reach.
Brennan's testimony at a June 16 Senate Intelligence Committee hearing came just days after an IS sympathizer shot and killed 49 people in an Orlando gay nightclub -- the worst mass shooting in U.S. history.
"We judge that ISIL is training and attempting to deploy operatives for further attacks," Brennan told the hearing, using another acronym for the group. "ISIL has a large cadre of Western fighters who could potentially serve as operatives for attacks in the West."
Brennan added that the IS group likely is attempting to smuggle militants into Western countries, possibly posing as refugees or through normal, legal travel.
He said that the group has suffered significant losses in Syria and Iraq but is nonetheless capable of carrying out attacks across the globe.
"Unfortunately, despite all our progress against ISIL on the battlefield and in the financial realm, our efforts have not reduced the group's terrorism capability and global reach," Brennan said.
"The resources needed for terrorism are very modest, and the group would have to suffer even heavier losses of territory, manpower, and money for its terrorist capacity to decline significantly," he added.
Brennan said that the CIA has not found any direct links between Omar Mateen, the 29-year-old gunman who carried out the June 12 massacre at the Pulse nightclub in Orlando, and any foreign terrorist organization though he pledged allegiance to the IS group during the attack.
Brennan called the attack in Orlando a "heinous act of wanton violence" and an "assault on the values of openness and tolerance" that are essential to the United States as a nation.
President Barack Obama and federal law-enforcement officials have said that Mateen, the son of immigrants from Afghanistan, appears to have been radicalized at least in part through extremist information disseminated on the Internet.
Brennan said in his June 16 testimony that the U.S.-led coalition fighting IS militants in Syria and Iraq is working to counter the group's "expansive propaganda machine."
He said the organization primarily uses the social media sites Twitter and Tumblr, as well as the messaging app Telegram, to disseminate its propaganda and that "it relies on a global network of sympathizers to further spread its messages."
Brennan said that he is concerned about Libya serving as a platform for IS militants to carry out attacks in Europe and elsewhere.
"The branch in Libya is probably the most developed and the most dangerous," he said. "We assess that it is trying to increase its influence in Africa and to plot attacks in the region and in Europe."
Asked about the broader security crisis in the region, Brennan said that Russia's military backing of Syrian President Bashar al-Assad has strengthened his hold on power.
"A year ago, [Assad] was on his back foot as the opposition forces were carrying out operations that were really degrading the Syrian military," he said. "He is in a stronger position than he was in June of last year."