Republican presidential candidate Donald Trump, who has called for expanded surveillance of American Muslims, is refusing to rule out extreme measures that include warrantless searches or faith-based identification requirements.

"We're going to have to do things that we never did before. Some people are going to be upset about it, but I think that now everybody is feeling that security is going to rule,” Trump told Yahoo News in an interview published Thursday. “And certain things will be done that we never thought would happen in this country in terms of information and learning about the enemy. And so we’re going to have to do certain things that were frankly unthinkable a year ago.”

When pressed on whether these measures might include tracking Muslim Americans in a database or noting their religious affiliations on identification cards, Trump would not go into detail -- but did not reject the options.

“We’re going to have to — we’re going to have to look at a lot of things very closely,” Trump said. “We’re going to have to look at the mosques. We’re going to have to look very, very carefully.”