An official on the National Security Council will tell lawmakers Tuesday he reported concerns about President Donald Trump’s position toward Ukraine to a top White House lawyer, according to a draft of his statement.

Lt. Col. Alexander Vindman, the top Ukraine expert on the National Security Council, will be the first White House official appearing for a Democrat-led impeachment inquiry of Trump who listened in on the president’s July 25 phone call with Volodymyr Zelensky, the Ukrainian president.