Sen. Claire McCaskill Claire Conner McCaskillMomentum growing among Republicans for Supreme Court vote before Election Day Democratic-linked group runs ads in Kansas GOP Senate primary Trump mocked for low attendance at rally MORE (D-Mo.) said early Sunday that any attempt by Russia to meddle in the United States presidential election would be “a form of warfare.”

“This should be not only about protecting us going forward, but this is a form of warfare,” McCaskill told ABC’s “This Week.”

McCaskill was responding to recent reports that that CIA concluded Russia tried to interfere in the presidential election to help Donald Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE win.

“For him to be trying to impact our election, he has to be held accountable,” she added, calling Russian President Vladimir Putin a "thug."

The Obama administration in October formally accused Russia of trying to meddle in the election. A recent report in The Washington Post says the CIA found that Russia was trying to help elect Trump.