Senate Minority Leader Chuck Schumer called on Defense Secretary Mark Esper to “do more” to protect those who have complained about President Trump, including Lt. Col. Alexander Vindman and Deputy Assistant Defense Secretary Laura Cooper, who will testify publicly this week during impeachment hearings.

“Recently, in response to questions from the media, you stated that LTC Vindman should not fear retaliation and that the Pentagon has protections for whistleblowers,” Schumer, a New York Democrat, wrote to Esper on Monday. “While I welcome your statement, I believe the Department of Defense must do more to formally ensure that all Department military and civilian personnel understand that they may make protected disclosures to Congress free from retaliation.”