A U.S. Army official and White House national security official plans to tell members of Congress conducting an impeachment inquiry that he was on the phone call between President Donald Trump and Ukraine’s leader in which Trump asked for an investigation into the Bidens, and that he raised concerns about it.

Lt. Col. Alexander S. Vindman, who is the top Ukraine expert on the National Security Council, considered the request so damaging to American national security that he reported it to a superior, according to his opening statement obtained by NBC News. The New York Times first reported the contents of his written statement.

Read the rest of the story at NBC News.