Senator John McCain (R-Ariz.), chairman of the Senate Armed Services Committee, told Martha MacCallum on the premiere of "The First 100 Days" that he is leaning toward voting to confirm Rex Tillerson for secretary of state.

McCain has previously voiced his reservations about Tillerson, the longtime CEO of ExxonMobil, and his relationship with Russian President Vladimir Putin.

"Some of my concerns have been satisfied, [but] I haven't made up my mind completely," McCain said.

"I just want him to have an understanding of the moral dimensions of Vladimir Putin in particular, and the slaughter that he has inflicted, and the violation of solemn treaties," he added.

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McCain called Putin a "butcher" and said "the only thing a thug understands is strength," adding that he hopes President-elect Donald Trump does not make the same "mistakes" past presidents have, in working in a more cordial way with the ex-KGB agent.

MacCallum pressed McCain as to whether he is considering supporting the confirmation of Tillerson, who has received the 'Order of Friendship' from Putin, and whose oil company has worked with Russia.

"Barely, yes," McCain said.

McCain also reacted to Trump's tweets about CIA Director John Brennan, after Brennan criticized the New Yorker.

"President-elect Trump is not fully aware of all of the activities and capabilities the Russians have developed," McCain said.

However, McCain said President Obama has received the same intelligence that Trump has and "done virtually nothing".

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