The victims, including women, children and entire families, were shot at close range in their own homes in Houla on Friday.
The massacre has drawn international outrage, and more than a half dozen countires have expelled Syrian diplomats in protest. The Obama administration expelled Syria's most senior envoy in Washington, D.C.
"We are at a tipping point," special envoy Kofi Annan told reporters Tuesday in Damascus, following a meeting with President Bashar Assad. "The Syrian people do not want the future to be one of bloodshed and division."
Government troops have been blamed for the attack, but Syrian leaders say terrorists were responsible. There has been no evidence to support the government's narrative nor has it given a death toll.
Houla activists reached by Skype said government troops shelled the area after anti-government protests and clashed with local rebels. Later, pro-government thugs known as shabiha from nearby villages swept through the area, stabbing residents and shooting them at close range.
The brutality of the killings and the high death toll raised new questions about the ability of a U.N.-brokered plan to end the violence in Syria, which began in March 2011. The unrest began with protests calling for political change, but government troops swiftly cracked down.
The Associated Press contributed to this report.