Defense Secretary Ash Carter says Islamic State fighters are trying to "consolidate their own footprint" in Libya by setting up training sites, drawing in foreign recruits and using the levers of economic power to raise money through taxes.

He says this is a great concern to the United States, saying IS must not be permitted to follow the formula it used in Iraq and Syria to capture large amounts of territory. In those cases the extremist group took advantage of civil war and sectarian divisions to assert themselves militarily with little opposition.

At a Pentagon news conference Thursday, Carter said he hopes Libyans are able to form a viable government that could take the lead in expelling Islamic State influences. He said the U.S. would support that effort.