Republican presidential candidate Ben Carson said he would not support a Muslim for president, stating that he believes a president’s faith matters and that Islam is not consistent with the Constitution.

“I would not advocate that we put a Muslim in charge of this nation. I absolutely would not agree with that,” he said in an interview broadcast Sunday on NBC’s “Meet the Press." Carson said earlier in the discussion that a president’s faith should not matter so long as its “within the realm of America and consistent with the Constitution, no problem.”

When host Chuck Todd pressed Carson on whether he believes “Islam is consistent with the Constitution,” Carson said, “No, I don't, I do not.”

The crowded field of GOP presidential candidates has faced repeated questions about the role of faith in presidential politics in recent days, after a controversial encounter between front-runner Donald Trump and a voter during a town hall in New Hampshire. The questioner told Trump, “We have a problem in this country. It’s called Muslims.” He also went on to accuse President Obama of lying about his Christian faith and stated that he does not believe the president was born in the United States.

When asked by Todd, Carson said he believes that the president is a Christian. “I believe that he is. I have no reason to doubt what he says,” the candidate responded.