She has described the Russian intervention in Ukraine as "a brazen violation of international law" after Ukrainian vessels were attacked by Russia in late November 2018. Cooper has been supportive of continued military aid to Ukraine. During a 2018 visit to Ukraine, she noted that Congress had authorized money for military aid, and she said that "one of my goals on this visit was to discuss with the Government of Ukraine what its priority needs are for security assistance." She met with Ukrainian Minister of Defence Stepan Poltorak to define measures of bilateral cooperation for defense. Cooper was the Pentagon official in charge of the aid package; she confirmed in December 2018 that the U.S. would have a comprehensive response to Russian aggression. In a video message Cooper said that Ukraine "can count on the U.S. to remain your strong partner" in strengthening its military. There is consensus that her assurances to the Ukrainians demonstrated that she expected the funds to be released in early 2019.