A whistleblower complaint released on Thursday said Volker met senior Ukrainian officials on how to "navigate" Trump's demands of President Volodymyr Zelensky. The complaint accused Trump of pressuring Zelensky in a July 25 phone call to supply dirt on former US vice president Joe Biden, the favorite to represent Democrats against Trump in the 2020 presidential election.
Committees in the Democratic-led House of Representatives ordered Volker to appear next Thursday to answer questions. In a letter released Friday, the lawmakers pointed to a tweet by Rudy Giuliani, Trump's personal lawyer, in which he showed a screenshot of a conversation in which Volker spoke of connecting him with a top adviser to Zelensky.