WASHINGTON - US President Barack Obama has nominated Robert Work, former undersecretary of the Navy, as next deputy secretary of defense, Pentagon chief Chuck Hagel announced Friday.

At a Pentagon news briefing, Hagel praised Work as "a highly respected and nationally recognized strategic thinker, practitioner, and expert on national security, as well as budgeting, technology, military affairs".

Work, currently the CEO of the Washington-based think tank Center for a New American Security, will succeed Ashton Carter, who resigned in last December.

"Bob's distinguished career of public service, his ability and his experience and knowledge of DOD (Department of Defense) make him uniquely qualified for his position," Hagel said, adding that Work would help lead the department "at a very, very challenging time".

Hagel was referring to the budgetary cuts faced by the Pentagon and the recent scandals involving the US nuclear missile forces, which have led to criticism and suspicion about the US military's ethics and behavior.

Work, 61, had spent 27 years in the US Marines before his retirement in 2001 to join the Center for Strategic and Budgetary Assessments, where he later became the vice president for strategic studies. He had served as undersecretary of the Navy from May 2009 to March 2013.