Ukraine commemorates the 30th anniversary of the Chernobyl disaster.
Russian president Vladimir Putin demands that NATO guarantee that it will not move its forces into Ukraine, accusing NATO and the U.S. of "trying to send Ukraine and Russia into direct armed conflict."
Acting U.S. Ambassador to Ukraine William B. Taylor Jr. testifies before Congress that he had been told President Donald Trump would, to help his reelection chances, withhold military aid to Ukraine until that country publicly declared investigations would be launched into Burisma Holdings, a company that hired former Vice President Joe Biden's son Hunter, as well as Ukraine's alleged involvement in the 2016 U.S. presidential election.
Twenty-one organizers for the Eurovision Song Contest in Kiev, Ukraine, resign en masse after claiming they were completely blocked from making decisions about the show. Despite the setback, the European Broadcasting Union insists that the event must go on.
U.S. Secretary of State John Kerry leaves for Moscow for talks on Syria and Ukraine with Russian President Vladimir Putin and Foreign Minister Sergey Lavrov on Wednesday. Kerry is also expected to discuss the case of Ukrainian pilot Nadiya Savchenko, who today was sentenced to 22 years in prison in the city of Donetsk.
The International Committee of the Red Cross (ICRC), guardian of the Geneva Convention, makes a confidential legal assessment that Ukraine is officially in a war, Western diplomats and officials say, opening the door to possible war crimes prosecutions, including over the downing of Malaysia Airlines Flight 17.