The United States said it was considering arming the Syrian rebels, as another massacre was reported.
Defence Secretary Chuck Hagel said handing weapons to the opposition was "an option".
It came as up to to 100 people were reported to have died in a "massacre" by Syrian forces.
The Syrian Observatory for Human Rights said soldiers loyal to President Bashar al Assad stormed the coastal village of Baida, with the dead including women and children.
The attackers used knives and guns, it was reported.
Responding to the reports, Defence Secretary Philip Hammond said: "The reports coming in of another massacre today, if they turn out to be true, will be another shocking chapter in this regime's book."
Hammond said the government was "strongly supportive" of the Syrian rebels, and said the regime had lost all legitimacy.
He also said there was a "quite compelling" case that chemical weapons, probably sarin, had been used in the fighting.
At a joint press conference with Hammond, Hagel said the US government was reconsidering its opposition to arming the rebels.
"Arming the rebels – that's an option," he said. "We must continue to look at options."