Sen. John McCain said Sunday that he's not entirely sure that has full confidence in President Trump.

While McCain said he had "utmost confidence" in Trump's administrative appointments like James Mattis, Michael Flynn and John Kelly, he could not bring himself to say the same thing about the new president.

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"I don't know because he has made so many comments that are contradictory," McCain said on ABC's "This Week with George Stephanopoulos."

"I think the fact that he's appointed and nominated these outstanding individuals is bound to be an encouraging sign," the Arizona Republican added. "I trust them, and I believe in them, and I've worked with them over many years."

McCain and Trump have long had a notoriously testy relationship. McCain has criticized Trump since the start of his presidential campaign for making comments that McCain has characterized as racist, sexist, and Islamophobic. McCain has also expressed concern about Trump's cozy relationship with Russian dictator Vladimir Putin. Trump, on the other hand, has ridiculed McCain for having been captured as a POW during the Vietnam War and characterized him as a weak politician.