Secretary of State Mike Pompeo fired a broadside at House Democrats on Tuesday, saying State Department officials scheduled to appear this week before committees conducting the impeachment inquiry would not be made available until “we obtain further clarity on these matters.”

The refusal, in a letter to House Foreign Affairs Committee Chairman Eliot L. Engel (D-N.Y.), described the demand for depositions by five officials who played a role in U.S. relations with Ukraine as “an attempt to intimidate, bully, and treat improperly, the distinguished professionals of the Department of State.”