Originally posted by the Voice of America. Voice of America content is produced by the Voice of America, a United States federal government-sponsored entity, and is in the public domain. Pompeo Criticized for Failing to Support Ousted US Ambassador to Ukraine Cindy Saine STATE DEPARTMENT - Several senior U.S. diplomats, including former Ambassador to Ukraine Marie Yovanovitch, are key witnesses in the impeachment inquiry into President Donald Trump. Trump is accused of having withheld U.S. military aid to Ukraine until that country's new president agreed to investigate one of Trump's political opponents, former Vice President and current presidential candidate Joe Biden. As transcripts from diplomats' closed-door Capitol Hill hearings are released, many are questioning why Secretary of State Mike Pompeo did not shield or even support Yovanovitch from an administration campaign that led to her eventual ouster. Then-U.S. Ambassador to Ukraine Yovanovitch told lawmakers in sworn testimony she was shocked to get a phone call in the middle of the night, telling her to leave her post and take the next plane home. WATCH: Cindy Saine's video report .