Republican presidential nominee Donald Trump is undermining America’s values with his campaign rhetoric and is unprepared to be commander-in-chief, President Barack Obama said during an interview that aired on CBS’ “Face the Nation” Sunday morning.

“If we start engaging in the kinds of proposals that we’ve heard from Mr. Trump or some of his surrogates like [former Republican House Speaker Newt] Gingrich where we start suggesting that we would apply religious tests to who could come in here, that we are screening Muslim Americans differently than we would others, then we are betraying that very thing that makes America exceptional,” Obama said.

Trump said he stood by his proposed ban on Muslim immigration in an interview on “Meet the Press” that aired Sunday, saying the seemingly tempered remarks he made on the matter during his convention address were actually “an expansion.”

Obama directed particular contempt at Trump’s statements that he would not defend Baltic NATO states if they were attacked by Russia.

“[NATO] was built by Democrats and Republicans and has been a cornerstone of U.S. foreign policy since the end of World War II,” Obama said. “And, you know for Mr. Trump, who has in the past suggested that America’s weak and not looking out for its allies, to then maybe not have enough information or understanding to go out and say that America might not stand by its solemn commitment to protect those same allies who stood with us after 9/11 when we were attacked, I think, is an indication of the lack of preparedness that he has been displaying when it comes to foreign policy.”

Host John Dickerson also asked Obama about Trump’s previous allegations that the president was not born in the United States, suggestions that have been repeatedly disproven.

“Well, I think it says something about what’s happened to the Republican Party over the course of the last eight, 10, 15 years,” the president said. “If you think about what a Bob Dole, or a Jim Baker, or a Howard Baker, or a Dick Lugar, or a Colin Powell stood for, yeah, they were conservative. They were concerned about limited government, and balancing budgets, and making sure we had a strong defense.”

Editor’s note: Donald Trump regularly incites political violence and is a serial liar, rampant xenophobe, racist, misogynist and birther who has repeatedly pledged to ban all Muslims ― 1.6 billion members of an entire religion ― from entering the U.S.