Sen. John McCain John Sidney McCainMomentum growing among Republicans for Supreme Court vote before Election Day McConnell urges GOP senators to 'keep your powder dry' on Supreme Court vacancy McSally says current Senate should vote on Trump nominee MORE (R-Ariz.) on Tuesday shot back at President Trump after Trump warned the Arizona Republican that, at some point, the president would "fight back."

"I've faced far greater challenges than this," McCain said, according to a CNN reporter.

In response to Trump's threat, McCain had this blunt response: "I’ve faced far greater challenges than this" https://t.co/nFo24e0dDe — Dan Merica (@danmericaCNN) October 17, 2017

The back-and-forth comes after McCain in a speech late Monday blasted “half-baked, spurious nationalism” in the United States.

ADVERTISEMENT

“To fear the world we have organized and led for three-quarters of a century, to abandon the ideals we have advanced around the globe, to refuse the obligations of international leadership and our duty to remain 'the last best hope of earth' for the sake of some half-baked, spurious nationalism cooked up by people who would rather find scapegoats than solve problems is as unpatriotic as an attachment to any other tired dogma of the past that Americans consigned to the ash heap of history,” McCain said after receiving the National Constitution Center's Liberty Medal.

Trump was asked about the remarks from McCain during a radio interview on Tuesday — and issued a warning.

"At some point, I fight back and it won't be pretty," Trump said on "The Chris Plante Show."

Trump, asked about McCain on @ChrisPlanteShow: "I'm being very, very nice. But at some point I fight back, and it won't be pretty." — Steven Portnoy (@stevenportnoy) October 17, 2017

McCain, who was diagnosed with brain cancer in July, served in the Navy for more than two decades and spent years as a prisoner of war in Vietnam.

Trump has attacked McCain in the past after he voted against a GOP bill to repeal and replace ObamaCare.