Defense Secretary nominee Mark Esper testifies before a Senate Armed Services Committee hearing on his nomination in Washington, U.S. July 16, 2019. REUTERS/Erin Scott

WASHINGTON (Reuters) - The U.S. Senate is due to vote next week to confirm Mark Esper as President Donald Trump’s second Secretary of Defense, ending the longest period by far that the Pentagon has been without a permanent top official.

The Senate Armed Services Committee approved Esper’s nomination during a closed meeting on Thursday. Senator Jim Inhofe, the panel’s Republican chairman, said he hoped the confirmation vote in the full Senate would begin as soon as Monday.

The vote breakdown in the committee was not made public.

Esper’s confirmation hearing on Tuesday was mostly smooth, except for a sharp exchange with Democratic Senator and presidential hopeful Elizabeth Warren, who said Esper should not be confirmed because of ethical concerns related to his former lobbyist job at defense contractor Raytheon Co.

Esper, 55, is expected to easily win confirmation in the Senate, where he has the support of many Democrats as well as Trump’s fellow Republicans. He has served a Secretary of the Army since November 2017.

There has been no confirmed defense secretary since Jim Mattis resigned in December over policy differences with Trump.

The armed services panel also voted to advance 1,231 other pending military nominations, including that of General Mark Milley to be chairman of the Joint Chiefs of Staff.