WASHINGTON — Defense Secretary Chuck Hagel confirmed Thursday that the Obama administration was rethinking its opposition to arming the rebels in Syria’s civil war, although he said that no decisions had been made.

“You look at and rethink all options,” Mr. Hagel said during a Pentagon news conference after being asked whether the administration was reassessing its stance on providing weapons to the rebels. He was joined by his British counterpart, Philip Hammond, whose government was early among close American allies to identify the possible use of chemical weapons during the civil war.

Although Mr. Hagel was the first senior American official to officially describe the administration’s decision to reassess providing arms to the opposition fighters, he emphasized that the process “doesn’t mean you do or you will.” But he said that “arming the rebels — that’s an option.”

Both his tone and his body language indicated that the assessment process would be careful and deliberate.