Getty Images(CNN) - There's a growing sense of alarm in Ukraine that it will be the victim of any prolonged political crisis in the United States over President Trump's controversial contacts with the new Ukrainian leader, Volodymyr Zelensky.
The first sign of trouble came with the resignation of the US special envoy to Ukraine, Kurt Volker.
Andriy Yermak, a top aide to President Zelensky, told CNN Saturday that Volker's "consistent and comprehensive support for Ukraine throughout his tenure means a lot for our country."
US military aid to Ukraine this year amounts to nearly $400 million, part of a program to rebuild the Ukrainian military so it can better counter pro-Russian separatists that control parts of eastern Ukraine.
Zelensky told Trump on the call that Ukraine wanted to buy more Javelin anti-tank missiles.