Ukrainian Lawmakers acknowledge the European Council President Donald Tusk after his speech at Ukraine's Parliament in Kiev on February 19, 2019. (Photo by Sergei SUPINSKY / AFP)

European Council President Donald Tusk, center, address to Ukrainian parliament in Kiev, Ukraine, Monday Feb. 19, 2019. (Mikhail Palinchak, Presidential Press Service Pool Photo via AP)

European Council President Donald Tusk address to Ukrainian parliament in Kiev, Ukraine, Tuesday, Feb. 19, 2019. (Mykola Lazarenko Presidential Press Service Pool Photo via AP)

Ukrainian President Petro Poroshenko, center, Prime Minister Volodymyr Groysman, right, and parliament speaker Andriy Parubiy show the newly signed Constitutional amendment to joining the EU and NATO in Ukrainian parliament in Kiev, Ukraine, Tuesday, Feb. 19, 2019. (Mikhail Palinchak, Presidential Press Service Pool Photo via AP)

European Council President Donald Tusk, center, address to Ukrainian parliament in Kiev, Ukraine, Monday Feb. 19, 2019. (Mikhail Palinchak, Presidential Press Service Pool Photo via AP)

Ukrainian President Petro Poroshenko (R) and Lawmakers acknowledge the European Council President Donald Tusk after his speech at Ukraine's Parliament in Kiev on February 19, 2019. (Photo by Sergei SUPINSKY / AFP)

Ukrainian Lawmakers acknowledge the European Council President Donald Tusk after his speech at Ukraine's Parliament in Kiev on February 19, 2019. (Photo by Sergei SUPINSKY / AFP)

Ukrainian Lawmakers acknowledge the European Council President Donald Tusk after his speech at Ukraine's Parliament in Kiev on February 19, 2019. (Photo by Sergei SUPINSKY / AFP)

Ukrainian Lawmakers acknowledge the European Council President Donald Tusk after his speech at Ukraine's Parliament in Kiev on February 19, 2019. (Photo by Sergei SUPINSKY / AFP)

European Council President Donald Tusk addresses the Ukraine's Parliament in Kiev on February, 2019. (Photo by Sergei SUPINSKY / AFP)

European Council President Donald Tusk addresses the Ukraine's Parliament in Kiev on February 19, 2019. (Photo by Sergei SUPINSKY / AFP)

Ukrainian Lawmakers acknowledge the European Council President Donald Tusk after his speech at Ukraine's Parliament in Kiev on February 19, 2019. (Photo by Sergei SUPINSKY / AFP)

Ukrainian President Petro Poroshenko (above) and the Lawmakers clap as they greet European Council President Donald Tusk prior to his address to Ukraine's Parliament in Kiev on February 19, 2019. (Photo by Sergei SUPINSKY / AFP)

Ukrainian Lawmakers acknowledge the European Council President Donald Tusk after his address to Ukraine's Parliament in Kiev on February 19, 2019. (Photo by Sergei SUPINSKY / AFP)

Ukrainian Lawmakers acknowledge the European Council President Donald Tusk after his address to Ukraine's Parliament in Kiev on February 19, 2019. (Photo by Sergei SUPINSKY / AFP)

Ukrainian President Petro Poroshenko (C), Prime Minister Volodymyr Groysman (R) and the Speaker of the parliament Andriy Parubiy, with the presence of European Council President (not seen), show amendments to the constitution signed by Poroshenko regarding the country's intentions to join the European Union and NATO in the Ukraine's Parliament in Kiev on February 19, 2019. (Photo by Sergei SUPINSKY / AFP)