Secretary of State Mike Pompeo on Tuesday pushed back on House Democrats' requests for his department's officials to testify on the Ukraine probe at the heart of their impeachment inquiry. In a letter to House Foreign Affairs Committee Chairman Eliot Engel, Pompeo said he'd use "all means at my disposal" to prevent what he called intimidation of State Department officials. Pompeo shared the letter on Twitter, where he wrote "I will not tolerate such tactics." He said the department would respond to the subpoena compelling him to produce documents by Oct. 4.