The United States and some of its Western allies accuse Russia of protecting the Assad regime to keep it in power.
U.S. officials are awaiting for Moscow to demonstrate its intentions about humanitarian relief efforts in Syria, said Marie Harf, a State Department spokeswoman.
When asked whether the Russians were playing for time as a diplomatic cover on behalf of Syria, Harf stated: "I don't want to guess what the motivations of the Russians are. We have said very clearly that if the Russians come out and talk about the importance of humanitarian access, they need to back up those words with actions."
So far, the only hint of progress in the talks has been a localized cease-fire to allow some evacuations and aid relief for the besieged city of Homs.
U.N. Emergency Relief Coordinator Valerie Amos said Friday that 1,400 people were evacuated from the Old City of Homs and 2,500 still there got relief supplies, but she lamented the bleak humanitarian situation throughout Syria.
"Civilians are under fire, and the social fabric of Syria has been torn to shreds," Amos said, adding that "all parties are failing in their responsibility to protect civilians."
In her statement on a briefing she gave the U.N. Security Council, Amos said: "No amount of words can adequately describe the horrific reality facing civilians."