Chuck Hagel: The U.S. Isn't Trying to Contain The Islamic State. It's Trying to Destroy It.

The Defense secretary says the U.S.'s mission is to "degrade and destroy the capability of ISIL to come after U.S. interests all over the world, and our allies."

After some confusion following a news conference Wednesday morning by President Obama, Defense Secretary Chuck Hagel tried to make clear that afternoon on CNN what the administration's goal is in its actions against the Islamic State in Iraq and Syria.

"It's not contain," Hagel told CNN's Jim Sciutto. "It's exactly what the president said: degrade and destroy."

But even then, there is still some question over just how much the Obama administration would like to see ISIS degraded. Hagel said that the mission is specifically to "degrade and destroy the capability of ISIL to come after U.S. interests all over the world, and our allies." Whether that means the administration would only be satisfied with a complete destruction of ISIS or if it would accept something that just leaves the group radically weakened is uncertain.

Hagel was not completely clear over just how great a threat ISIS poses right now to U.S. interests, particularly within U.S. territory. "We are aware of over 100 U.S. citizens who have U.S. passports who are fighting in the Middle East with ISIL forces," he said. "There may be more, we don't know." But that doesn't necessarily mean there is a direct threat from ISIS right now to the homeland.

"We know they're a threat," Hagel said, without saying whether or not there is a specific threat to the U.S. homeland. "We know they're brutal. We know they are ... something that we have never seen before ... there's a dangerous, dangerous ideology of brutality of a barbaric nature that we have not seen before. So my job as secretary of Defense is not to second-guess what may be or what's going to be."

That isn't at all to say the Defense secretary underplayed how potentially dangerous ISIS could be to the United States and its allies. "This crowd is as dangerous a group of people, beyond just terrorists, they are an army, marrying this with an ideology and a capacity to do things," he said. "They control half of Iraq today. They control half of Syria today. We better be taking them seriously."

"You've got to destroy it," Hagel said later. "Because if we don't destroy it, it will get worse." CNN's Sciutto later asked Hagel if he would "vow" that ISIS would be destroyed, not "just degraded or contained."

"Well, vows are something beyond my mortal capacity of doing," Hagel responded. But, he said, "We will do everything possible that we can do to destroy their capacity to inflict harm on our people and western values and our interests."

Emma Roller contributed to this article.