Pentagon chief vows to cooperate with impeachment probe

US Defense Secretary Mark Esper said Sunday the Pentagon would cooperate with the congressional impeachment inquiry -- in an apparent break with President Donald Trump's policy to thwart the probe.Esper said his department would try to comply with a subpoena from House Democrats seeking records relating to the withholding of US military aid to Ukraine."We will do everything we can to cooperate with the Congress," Esper said on CBS's Face The Nation.