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Story highlights

President Barack Obama defended his strategy for fighting ISIS in a press conference Monday

Obama also stood by comments he made Friday saying ISIS had been contained

Obama also slammed Republican critics who have called for increased scrutiny -- if not outright banning of allowing refugees to enter parts of the U.S.

(CNN) —  

President Barack Obama sharply defended his strategy Monday for going after ISIS amid mounting criticism that the U.S. is not doing enough to stop the terror organization that went on a killing spree in Paris last week.

He faced a barrage of tough and probing questions from international journalists at a G20 summit in Antalya, Turkey, that often put him on the defensive. In response, he repeatedly stressed confidence in his approach to combating terrorism and handling Syria, where a civil war has dogged his administration for years and helped create an opening for ISIS to flourish.

“We have the right strategy and we’re going to see it through,” Obama said. “There will be an intensification of the strategy we have put forward, but the strategy we have put forward is the strategy that will ultimately work” though it will take time.

He said that airstrikes by the U.S.-led coalition have been effective in taking out key members of the terror group’s leadership and that a large presence of ground troops in Syria would be a “mistake.”

An increasing chorus of critics, especially in the GOP, have called for a more aggressive U.S. military effort in fighting ISIS, but Obama pushed back against that call.

“It is not just my view but the view of my closest military and civilian advisers that that would be a mistake,” Obama said, adding that’s “because we would see a repetition of what we’ve seen before, which is if you do not have local populations that are committed to inclusive governance and who are pushing back against ideological extremes, that they resurface, unless we’re prepared to have a permanent occupation of these countries.”

Last month, Obama committed to sending “less than 50” Special Operations forces to the region to fight ISIS, also know as ISIL.

Obama used much of the press conference to strike back at his critics, sounding at times defensive and combative. His tone also contrasted with that of French President Francois Hollande, who was speaking at the same time in France.

“France is at war,” Hollande declared, indicating he would ask parliament to impose a three-month-long state of emergency.

Obama, for his part, justified his use of the term “contained” last week to describe the ISIS threat, a remark he made in an interview that aired just hours before the Paris terror attack.

“When I said that we are containing their spread in Iraq and Syria, in fact they control less territory then they did last year and the more we shrink that territory, the less they can pretend that they are somehow a functioning state,” Obama said Monday. “And the more it becomes apparent that they are simply a network of killers who are brutalizing local populations that allows us to reduce the flow of foreign fighters, which then over time will lessen the numbers of terrorist who can potential carry out terrible acts like they did in Paris.”

He was also dismissive of those who “seem to think that if I were just more bellicose in expressing what we’re doing, that would make a difference.”

Instead, he said, “We’ll do what is required to keep the American people safe.”

He continued, “if folks want to pop off and have opinions about what they think th