Anchored by Jake Tapper, The Lead airs at 4 p.m. ET on CNN.
The latest on the crisis in Ukraine, plus a look at the key 2014 Senate races.
(CNN) - The city of Kiev is literally on fire and Sen. John McCain says as the situation escalates, the United States needs to be wary of an old foe.
"Watch out for Vladimir Putin because he will try to make mischief because he believes that Ukraine is part of Russia," McCain told CNN's "The Lead with Jake Tapper."
"We have to side with the protesters and the power has to be dispersed from the hands of (Ukrainian President Viktor) Yanukovych, who changed the constitution and put virtually all power in the hands of the President," said McCain.
Last month, Putin said Russia would honor loans it committed to Ukraine, despite the turmoil – a move McCain views with suspicion.
"Obviously, he's not a man known for his generosity," said McCain. "We really need to know what was behind that. But most of all, I think we need to understand that Vladimir Putin really is committed to this whole idea of the Russian empire, or the Russian near, abroad."
The Arizona Republican and member of the Senate Foreign Relations Committee said that he does not know what Putin will do, but "nothing would surprise me."
"We ought to tell Putin that interference ... in the ways that he might do it, would be totally unacceptable to the United States," said McCain.
Also unacceptable for McCain, is what he described as a lack of U.S. action in this case. He called on President Barack Obama to take clear action to address the situation.
"The President should be working with Congress to prepare a set of sanctions against Ukraine that would be put into effect unless this comes to a halt," said McCain.
For more of our interview with Sen. John McCain, including his analysis of chaotic protests in another hemisphere – Caracas, Venezuela – watch the video above.