WASHINGTON – Chuck Hagel, the likely next secretary of defense, would be the first to enter the Pentagon having publicly advocated for sharply reducing the number of U.S. nuclear weapons, possibly without equivalent cuts by Russia. He supports an international movement called Global Zero that favors eliminating all nuclear weapons.

That puts him outside the orthodoxy embraced by many of his fellow Republicans but inside a widening circle of national security thinkers — including President Obama — who believe nuclear weapons are becoming less relevant to 21st-century security threats like terrorism.

“Sen. Hagel certainly would bring to office a more ambitious view on nuclear reductions than his predecessors,” said Steven Pifer, a senior fellow at the Brookings Institution. “While he would likely take a less dramatic position in office, it might not be a bad thing to have a secretary of defense question what nuclear deterrence requires today.”

The customary stance of defense secretaries in the nuclear age has been that the weapons are a necessary evil.

Hagel, 66, takes a subtly different view — one shared by Obama but opposed by those in Congress who believe disarmament is weakness and that an outsized American nuclear arsenal must be maintained indefinitely as a counterweight to the nuclear ambitions of anti-Western countries like North Korea and Iran.

Hagel argues for doing away with nuclear weapons entirely, but not immediately and not unilaterally.