WASHINGTON –

President Barack Obama ruled out dispatching a major U.S. ground force against Islamic State in Syria and Iraq, saying it would be a "serious mistake" that would lead the nation into an unsustainable strategy requiring a long-term occupation in the region.

Obama called the Islamic State terror organization "the face of evil" and insisted the U.S. and its allies are shrinking its hold in Syria and Iraq even as the extremist group has demonstrated its ability to commit violence beyond the region.

The deadly attacks in Paris last week were "a terrible and sickening setback" in what will be a long campaign against Islamic State, Obama said Monday, shortly after meeting with leaders of European countries at a summit in Turkey.

The U.S. will continue a strategy that concentrates on military power, in the form of airstrikes and working with local forces, economic pressure and attempts to stabilize failed states where the group has thrived, Obama said. He also said the U.S. would streamline intelligence sharing with France to give French authorities more timely information.

What won't work, he said, is sending thousands more U.S. troops into the fight.

"We would see a repetition of what we've seen before, which is if you do not have local populations that are committed" to helping combat extremism, Obama said, the terrorists "resurface, unless we are prepared to have a permanent occupation of these countries."

The terrorist attacks in Paris last Friday, which left at least 129 dead and more than 300 wounded, dominated the meeting of leaders from the world's 20 biggest economies in Antalya, Turkey. The G-20 leaders, including Russian President Vladimir Putin, pledged to redouble efforts to cut off financing for terror groups and disrupt recruitment efforts.

The U.S. and Russia are working with other powers in the region on a plan to stabilize Syria, intended to bring about a political resolution of that country's four-year-old civil war. Islamic State has taken advantage of the conflict there to seize territory and recruit worldwide.

The U.S. has already begun working with France and other countries since Saturday to step up airstrikes against the group in Iraq and Syria. Obama met Monday with U.K. Prime Minister David Cameron, German Chancellor Angela Merkel, Prime Minister Matteo Renzi of Italy and French Foreign Minister Laurent Fabius on the next steps in the fight.

The intelligence sharing agreement with France that Obama announced allows for easier sharing of operational planning data, Navy Capt. Jeff Davis, a Pentagon spokesman, said. The change had been "in the works for a while" and was accelerated after the attacks in Paris, he said.

Airstrikes France conducted Sunday against Islamic State were targeted by the French military based on information the U.S. shared with them under the new arrangement, Davis said.

Obama lit into his domestic critics, particularly some Republicans running in the 2016 presidential campaign who've called for a more robust military campaign against Islamic State.

"Some of them seem to think that if I were just more bellicose in expressing what we're doing that that would make a difference because that seems to be the only thing that they're doing, is talking as if they're tough," Obama said.

Republican critics have offered few concrete alternatives, he said, with the exceptions of sending in ground forces or establishing no-fly zones, moves that open up a "whole set of questions that have to be answered."

The president grew visibly irritated with repeated questions during his news conference about whether he should act more decisively or faster to destroy Islamic State. He said he is aware his approach doesn't offer the satisfaction of a "neat headline" or an immediate solution.

"What I'm not interested in doing is posing or pursuing some notion of 'American leadership' or 'America winning"' that has "no relationship to what is actually going to work," he said.

Obama also rejected building sentiment in the U.S. to turn back refugees from Syria out of fear that terrorists will hide among them. He called suggestions by some Republicans that the U.S. accept only Christian refugees "shameful."

"Many of these refugees are the victims of terrorism themselves. That's what they're fleeing," he said. "Slamming the door in their faces would be a betrayal of our values."

He offered assurances that the refugees allowed into the U.S. are accepted "only after subjecting them to rigorous screening and security checks."

He said countries bordering Syria such as Turkey, Lebanon and Jordan "are already bearing an extraordinary burden" from the flow of refugees and "cannot be expected to do so alone."