Republican presidential candidate Donald Trump said Sunday that he would rule out putting American Muslims in internment camps.

“Would you categorically rule out the idea of internment camps for American Muslims?” ABC News’ “This Week” host Jonathan Karl asked Trump.

“I would rule it out, but we would have to be very vigilant. We’re going to have to be very smart,” Trump said. “We’re going to have to be very rigid, very vigilant. And if we’re not very, very strong and very, very smart, we have a big, big problem coming up. We’ve already had the problem. Check out the World Trade Center, OK.”

“Check out the Pentagon,” he continued. “We’ve already had the problem.”