U.S. Defense Secretary Chuck Hagel acknowledged on Thursday that his government is no longer ruling out arming Syrian rebels, BBC reports.
It is the first time a senior U.S. official has said openly that the U.S. is reconsidering its opposition to supplying weapons to rebel forces.
Last year, President Barack Obama rejected the proposal made by then Secretary of State Hillary Clinton.
Speaking in Washington at a joint news conference with British Defense Secretary Philip Hammond, Hagel confirmed the U.S. was reconsidering its opposition to providing weapons to rebels, but stressed that no decision had been made yet.
"Arming the rebels - that's an option," he told reporters, according to the BBC.
"You look at and rethink all options. It doesn't mean you do or you will. These are options that must be considered with the international community: what is possible, what can help accomplish [our] objectives," he added.
Hammond said the UK had so far been unable to provide weapons because of an EU ban on arming the rebels.
But "we will look at the situation when that ban expires in a few weeks' time," he added, according to the BBC.
U.S. allies such as Qatar and Saudi Arabia are already providing weapons to various groups fighting President Bashar al-Assad's forces.
The pressure to act has intensified in recent days after emerging evidence that Syria has used chemical weapons such as the nerve gas sarin.
Hagel and his British counterpart indicated that existent evidence of alleged chemical weapon was not sufficient to trigger an international response.
Hammond said the public still remembered that claims of weapons of mass destruction, which led to the Iraq invasion in 2003, turned out to be incorrect.
"There is a very strong view that we have to have very clear, very high-quality evidence before we make plans and act on that evidence," he said.
"If there were future use of chemical agents, that would generate new opportunities for us to establish a clear evidence of use to a legal standard of evidence."
Many in the West have raised concerns about arming the rebels, fearing weapons could end up in the hands of radical Islamist groups such as the Al-Nusra Front, which this month pledged allegiance to Al-Qaeda.
Washington has been gradually shifting its policy on providing assistance to the opposition, with Secretary of State John Kerry announcing at the last Friends of Syria meeting in February that the U.S. would start providing direct non-lethal aid to rebel fighters.
Britain and France had been pushing for a European Union arms embargo to be allowed to expire by the end of May. Paris has since appeared more wary about arms supplies since the Al-Qaeda pledge from Al-Nusra.