US President Barack Obama has nominated Ashton Carter, a former deputy defence secretary, to be his next defence secretary, replacing Chuck Hagel.
Carter, 60, has support among Republicans who will take control of the Senate next month and decide on his confirmation.
Reporting from Washington after a news conference by Obama announcing his defence nominee, Al Jazeera's Patty Culhane said that Carter is an interesting choice for the position because Hagel was reportedly forced out for the reason that the US needed someone with a different set of experiences.
"But Carter does not have a lot of experience in the Middle East, where the Islamic State of Syria and the Levant (ISIL) poses one of the biggest challenges faced by the military at the moment," she said.
"It's interesting that he is being heralded as having all this experience. I've spoken to people behind the scenes who say he's a fast learner."
Carter has gained a reputation as an expert on hi-tech weapons and military budgets, portraying himself as a reformer intent on making the vast Pentagon bureaucracy more efficient.
While Carter is skilled in weapons programmes and technological trends, he has less experience overseeing war strategy and has never served in uniform - unlike Hagel who served in the military and was wounded in the Vietnam War.
An academic by training and a holder of a doctorate in theoretical physics from the University of Oxford, Carter worked in the Pentagon during Bill Clinton's presidency, overseeing nuclear arms policies and helped with efforts to remove nuclear weapons from Ukraine and other former Soviet territories.
A former professor at Harvard University's Kennedy School of Government, Carter served as the Pentagon's top weapons buyer from 2009 to 2011 and then as deputy defence secretary until 2013.
Source: Al Jazeera and agencies