UN rights chief Navi Pillay has renewed a demand that the divided security council order an International Criminal Court war crimes investigation in Syria.
Her call added to a petition by 58 countries calling for a war crimes case to be started.
But Pillay said after a closed council meeting that she saw little sign that the 15-member body, badly split over the 22-month-old conflict, was ready to take a decision.
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"I firmly believe that war crimes and crimes against humanity have been committed, are being committed and should be investigated," Pillay told reporters on Friday.
"I have urged the security council to refer the situation to the International Criminal Court for investigation of war crimes and crimes against humanity on the part of all parties engaged in this conflict," she said.
Highlighting the UN estimate that more than 60,000 people have been killed in Syria, Pillay said victims in Syria "see the situation as the United Nations not carrying out its responsibility to protect victims".
Syria is not an ICC member and the security council is the only body which can refer the conflict to the court.
Russia and China have used their power as permanent members of the security council to block three resolutions that would have threatened sanctions against Syria's President Bashar al-Assad and in some cases a war crimes case.
Diplomats at the council meeting said there was discussion of the calls for an ICC investigation but still opposition from Russia and its allies.
Ambassadors from council members Australia, Britain, France, Luxembourg, South Korea spoke after the meeting to back the petition drawn up by Switzerland calling for the investigation.
UN leader Ban Ki-moon has warned that Syria is in a "death spiral", as his top humanitarian and human rights officials pleaded with the security council to take firmer action.
"You have seen the tragedy play out on your television screens," Ban said on Friday, in a speech at Stanford University in California ahead of the closed security council meeting.
"Syria is in a death spiral," he said, highlighting the more than 60,000 people killed in a war that will soon enter its third year.
On top of the humanitarian crisis, a split between opponents and supporters of al-Assad has deadlocked efforts to reach a political end to the conflict.
Ban said there were "deep divisions" between countries in the region and on the 15-member security council.
"We are still a long way from getting the Syrians together to make the key decisions that only they can make," the UN secretary-general said, adding his voice to those who have called on the security council to act.
The UN expects the number of refugees outside the country to nearly double by June to 1.1 million people. There are now more than 640,000 in camps in Jordan, Lebanon, Iraq, Turkey and Egypt.
