Central Intelligence Agency Director John Brennan told the Council on Foreign Relations in New York October 23, 2015 about the U.S. position in Syria:

The U.S. doesn’t want to see Syrian President Bashar al-Assad’s government collapse and create a vacuum for Islamic State and other militants to take over.

What we don’t want to do is to allow those extremist elements, including Islamic State, Jabhat al-Nusra, and al-Qaeda elements within Syria, to seize power from a collapsed regime.

The last thing we want to do is to allow them to march into Damascus.

He dismissed the extremists’ claims to represent a purist form of Islam.:

The extremists are terrorists, they’re criminals. Most of them are psychopathic thugs, murderers who use a religious concept and masquerade and mask themselves in that religious construct.

The future governance of Syria is not going to be resolved on the battlefield and needs a political solution.

We need to continue to support those elements within Syria that are dedicated to moving Assad out, but there has to be some kind of political pathway to the future.

The overall threat of terrorism is greatly amplified by today’s interconnected world, where an incident in one corner of the globe can instantly spark a reaction thousands of miles away, and where a lone extremist can go online and learn how to carry out an attack without ever leaving home.