The main United Nations human rights body denounced Syria on Thursday for what it claimed were crimes against humanity.
With a more than three-quarters majority, the Geneva-based forum adopted a resolution, calling for an end to the violence against civilians.
The US said Russia and China, who voted against the motion, were “on the wrong side of history”.
“There is an overwhelming international consensus about the human rights situation in Syria and, in fact, the humanitarian crisis that has been created by the Assad regime,” said Eileen Chamberlain Donahoe, US Human Rights Ambassador to the UN.
The resolution comes after the UN’s humanitarian aid chief Valerie Amos was refused entry to Syria, and following an announcement that UN and Arab League envoy Kofi Annan would visit the country shortly.
The Council voiced strong concern about the deteriorating humanitarian situation, calling for food, medicine and fuel to be sent to besieged cities.
Meanwhile Britain pulled its diplomats out of Syria on Thursday, citing security reasons.
However the UK’s Foreign Office said London had not broken diplomatic ties with Damascus.