ANTALYA, Turkey (CBSDC/AP) — President Barack Obama said during a news conference Monday that the best way to take out the Islamic State of Iraq and Syria is through strategy and not a “neat headline.”

Responding to CNN’s Jim Acosta’s question of “why can’t we take out these bastards,” Obama said they need to tackle the underlying elements of why people join terror groups, on top of taking out ISIS itself.

“This is not, as I said, a traditional military opponent. We can retake territory. And as long as we leave our troops there, we can hold it, but that does not solve the underlying problem of eliminating the dynamics that are producing these kinds of violent extremist groups,” the president said during the G20 summit in Turkey. “And so we are going to continue to pursue the strategy that has the best chance of working even though it does not offer the satisfaction, I guess, of a neat headline or an immediate resolution.”

Obama continued, “And part of the reason, as I said, because there are costs to the other side. I just want to remind people. This is not an abstraction. When we send troops in, these troops get injured, they get killed, they’re away from their families. Our country spends hundreds of billions of dollars. And so given the fact that there are enormous sacrifices involved in any military action, it’s best that we don’t, you know, shoot first and aim later. It’s important for us to get the strategy right and the strategy that we are pursuing is the right one.”

Calling the Paris terror attacks a “terrible setback,” the president stated more nations “need to step up” in the fight against ISIS.

“Tragically Paris is not along. We’ve seen outrageous attacks by ISIL in Beirut, last month in Ankara, routinely in Iraq. Here at the G20 our nations have sent an unmistakable message: That we are united against this threat. ISIL is the face of evil,” he said. “Our goal, as I’ve said many times, is to degrade and ultimately destroy this barbaric terrorist.”

However, Obama said, using a large number of U.S. troops on the ground to combat ISIS would be “a mistake.” He said the same view is held by his closest military and civilian advisers.

Obama added that the U.S. will still take in Syrian refugees “only after subjecting them to rigorous screening and security checks.”

He then hit back at Republican presidential candidates who have said the U.S. should only allow Syrian Christians to enter.

“That’s shameful,” Obama said. “That’s not American. That’s not who we are.”

The terror attacks in Paris on Friday left 129 dead, and 350 others wounded.