US Secretary of State Hillary Clinton, who was heading to an international security conference in Munich, planned to speak by phone with Russian Foreign Minister Sergei Lavrov about it later in the day on Friday amid a US push for passage of the resolution, the official said.
"We're cautiously optimistic," the official, who spoke on condition of anonymity, said about winning Russia's support.
The latest draft does not explicitly call on Syrian President Bashar al-Assad to step down or mention an arms embargo or sanctions, though it "fully supports" an Arab League plan to facilitate a democratic transition.
"From our perspective, this meets the objective of supporting the demands of the Syrian people and the Arab League... providing a peaceful Syrian-led political path forward," a senior State Department official said on Friday.
