Jim Michaels

USA TODAY

The Islamic State's ability to launch terror strikes remains a "formidable" threat despite military successes against the militant group in Iraq and Syria, CIA Director John Brennan said Thursday.

As the extremist group has lost territory in Iraq and Syria it has redoubled its efforts to encourage so-called lone wolf attacks or infiltrate operatives to strike targets outside the region, he said.

“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 told the Senate Intelligence Committee, using an acronym for the Islamic State. “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 said.

Intelligence and law enforcement officials believe Omar Mateen, the gunman who killed 49 people Sunday in an Orlando gay nightclub was a lone wolf. The assailants are inspired by extremism and are difficult to identify before they attack.

“We have not been able to uncover a direct link between that individual Mateen and a foreign terrorist organization but that inspiration can lead someone to embark on this path of destruction,” Brennan said.

Mateen claimed allegiance to the Islamic State as he carried out the attack, the worst mass shooting in U.S. history.

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The Islamic State’s massive propaganda operation has been successful in encouraging attacks throughout the world and in pushing the militants out of territory has not reduced their ability to recruit on the Internet. The group will also probably increase efforts to send operatives outside the region to launch attacks, Brennan said.

"The group is probably exploring a variety of means for infiltrating operatives into the West, including refugee flows, smuggling routes and legitimate methods of travel," he said.

The Pentagon has also acknowledged the militants are resorting more to terrorism as a means of remaining relevant as they suffer battlefield losses. The U.S.-led coalition has launched thousands of airstrikes against the militants and is supporting Iraq's security forces and a coalition of fighters in Syria who have pledged to attack the Islamic State.

The Islamic State has been expelled from about 45% of the territory it once controlled in Iraq. Militants have been pushed from about 20% of the territory in Syria.

Coalition airstrikes have reduced the Islamic State’s oil revenues by as much as 50% and destroyed about $500 million in cash, the Pentagon said.

But Brennan said the militant organization is adapting to the battlefield setbacks.

“ISIL is adapting to the coalition’s efforts, and it continues to generate at least tens of millions of dollars in revenue per month, primarily from taxation and from crude oil sales,” he said.