President Barack Obama is rejecting the notion that the United States has underestimated the ability of the Islamic State group in the wake of the deadly terror attacks in Paris.

Obama says the danger of the group is the reason the U.S. is operating in Iraq and Syria, and why it has mobilized 65 countries to go after IS.

Obama says one of the challenges of terrorism is to understand that a handful of people who don't mind dying can kill a lot of people.

The president says reducing the territory controlled by the group in Iraq and Syria will reduce the flow of fighters and lessen the threat it poses. He says disrupting the threat requires constant vigilance and communication. Obama spoke at a news conference Monday in Antalya, Turkey.