McCain Doesn't Know if He Has 'Utmost Confidence' in President Trump John McCain also reveals he'll vote for Trump's secretary of state nominee.

 -- Sen. John McCain praised President Donald Trump's cabinet picks and revealed he will vote in favor of Rex Tillerson, Trump's pick to lead the State Department, despite concerns about the nominee's relationship with Russian President Vladimir Putin.

"I will be voting in favor of his nomination," McCain said of Tillerson in an interview Sunday with ABC News' George Stephanopoulos on "This Week."

"Listen, this wasn't an easy call. But I also believe that when there's doubt the president, the incoming president, gets the benefit of the doubt, and that's the way I've treated every president that I've had the obligation to vote for or against as a member of the United States Senate."

Sen. John McCain and his fellow Republican foreign policy hawk Sen. Lindsey Graham released a joint statement today supporting Tillerson's nomination.

""After careful consideration, and much discussion with Mr. Tillerson, we have decided to support his nomination to be secretary of state. Though we still have concerns about his past dealings with the Russian government and President Vladimir Putin, we believe that Mr. Tillerson can be an effective advocate for U.S. interests," the statement said.

But, another prominent Republican senator has still apparently not made up his mind on Tillerson.

Sen. Marco Rubio of Florida, a key member of the Senate Foreign Relations Committee who sharply questioned Tillerson on Russia's involvement in Syria during the confirmation hearing, has not decided whether to vote for Tillerson, according to Foreign Relations Committee Chairman Bob Corker of Tennessee, who spoke to Rubio on Friday.

Rubio has met with Tillerson privately since the hearing, the senator's office said. He's also met with Vice President Mike Pence on the subject, according to Corker.

Wihtout Rubio's vote, Tillerson's nomination would not move out of committee. Republican leadership could still hold a full Senate vote and confirm him, especially now that he has McCain and Graham's public support, but it would be an embarrassing bruise for Trump administration.

McCain also praised some of Trump's other Cabinet picks on "This Week," saying he has the "utmost confidence" in Trump's national security team, in particular.

"I have the utmost confidence in Gen. Mattis, Gen. Flynn, Gen. Kelly, Dan Coats. I couldn't have picked a better team," he said.

But, the Arizona senator did not have the same praise for the president himself.

Asked by Stephanopoulos if he has the "utmost confidence" in the commander-in-chief, McCain, who chairs the Senate Armed Services Committee, replied, "I don't know because he has made so many comments that are contradictory."

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