Defense Secretary Lloyd Austin on Monday criticized Republican Sen. Tommy Tuberville’s ongoing hold on hundreds of military promotions as an “unprecedented” move that threatens the country’s safety.

“Because of this blanket hold, starting today, for the first time in the history of the Department of Defense, three of our military services are operating without Senate-confirmed leaders,” Austin said during a relinquishment ceremony for the chief of naval operations, Adm. Mike Gilday, at the U.S. Naval Academy in Annapolis, Maryland.

“This is unprecedented, it is unnecessary, and it is unsafe,” he added. “This sweeping hold is undermining America’s military readiness. It’s hindering our ability to retain our very best officers. And it’s upending the lives of far too many American military families.”