Sen. John McCainJohn Sidney McCainHow House Republicans scrambled the Russia probe The Hill's 12:30 Report The Hill's Morning Report - Sponsored by CVS Health - A pivotal day for House Republicans on immigration MORE (R-Ariz.) said President Obama’s lack of understanding of Vladimir Putin was to blame for the United State’s weak response to the Russian invasion of Ukraine.

“This president does not understand Vladimir Putin,” McCain said on the Senate floor Tuesday. “It’s time this administration woke up about Vladimir Putin.”

Russian forces have entered Ukraine after an uprising ousted the Russian-backed leader, Viktor Yanukovych. McCain said the U.S. shouldn’t have expected anything else from a former KGB operative.

Putin said military intervention was needed to protect Russian-speaking people living in Ukraine, but McCain said this line of reasoning would also allow Russia to invade other countries such as Poland and Moldova, among others. 

“We need to act. We need to speak up for the people being taken over by Vladimir Putin’s army,” McCain said. “If we allows Mr. Putin to assert his authority over these areas because there are Russian speaking people, that message is not missed [by other countries].”

The administration has offered $1 billion in aid to Ukraine and threatened U.S. sanctions against Russia if its army doesn’t leave the country.