Lt. Col. Alexander Vindman, the National Security Council's top Ukraine expert, is set to testify that he conveyed concerns internally to officials after listening to President Trump's phone call with his Ukrainian counterpart Volodymyr Zelensky, the New York Times first reported Monday.
Why it matters: Vindman, a decorated Iraq War veteran, would be the first official from the White House who listened to the July 25 call between Trump and Zelensky discussing former Vice President Joe Biden and his son Hunter Biden, which resulted in a formal impeachment inquiry being launched against the U.S. commander in chief.
The big picture: Politico obtained a copy of his opening statement ahead of his testimony before House impeachment investigators Tuesday.
Read Vindman's statement:
Go deeper: Trump-Ukraine scandal: All the key players, dates and documents
Editor's note: This article has been updated with Vindman's opening statement.
