National Security official Lt. Col. Alexander S. Vindman plans to testify before Congress on Tuesday that he was listening to the phone call between President Trump and Ukrainian President Volodymyr Zelenskiy. Vindman plans to tell Congress that he reported concerns about the call, saying in his opening statement: "I was concerned by the call. I did not think it was proper to demand that a foreign government investigate a U.S. citizen, and I was worried about the implications for the U.S. government’s support of Ukraine."