The United States is rethinking its opposition to arming the Syrian rebels, US Defence Secretary Chuck Hagel has said.
Hagel stressed that no decision by US President Barack Obama had been made and did not signal whether one was likely soon.
US military commanders have voiced concerns that weapons could fall into the hands anti-American Islamic extremists and that arming opposition groups may do little to end the conflict.
"You look at and rethink all options. It doesn't mean you do or you will" choose them, Hagel said.
"These are options that must be considered with partners, with the international community: what is possible, what can help accomplish (our) objectives," he added.
British defence secretary Philip Hammond, who is in Washington for talks, noted that the UK was constrained by a European Union ban on supplying armaments to the rebels.
He said: "Both of our nations will only do what we legally can do," Hammond said, adding his government would "look at the situation when that ban expires in a few weeks' time."