Donald Trump is considering the possibility of setting up a commission to “take a very serious look” at radical Islamic terrorism and his proposals to temporarily bar Muslims from entering the United States, even floating the name of former New York City mayor Rudy Giuliani to spearhead the operation.

“We have to be extremely careful,” Trump told Fox News in a phone interview Wednesday when asked about his calls for a Muslim ban. “In fact, I’m thinking about setting up a commission perhaps headed by Rudy Giuliani to take a very serious look at this problem. But this is a worldwide problem. And we have to be smart.”

Giuliani, who was New York City’s mayor during the terrorist attacks that hit the World Trade Center on September 11, 2001, endorsed Trump last month, ahead of the New York primary.

“I’m Rudy Giuliani. I mean a lot in New York politics. I endorse Donald Trump, but I’m not a part of the campaign,” the former mayor told CNN in April.