Friday: Marie Yovanovitch, the former U.S. ambassador to Ukraine. She was ousted from her post in May.
Nov. 19, morning: Jennifer Williams, a special adviser to Vice President Mike Pence for Europe and Russia, and Lt. Col. Alexander Vindman, director for European affairs at the National Security Council.
Nov. 19, afternoon: Kurt Volker, the former U.S. special envoy to Ukraine, and Tim Morrison, a White House aide with the National Security Council.
Nov. 20, morning: Gordon Sondland, U.S. ambassador to the European Union.
Nov. 20, afternoon: Laura Cooper, deputy assistant secretary of defense for Russian, Ukrainian and Eurasian affairs, and David Hale, undersecretary of state for political affairs.
Nov. 21, morning: Fiona Hill, former National Security Council senior director for Europe and Russia.