Russia on Monday said the Syrian authorities were prepared to hold talks in Moscow to end escalating violence but the opposition refused to come to the table unless President Bashar al-Assad stepped down.
Russia, which has resisted Western calls to back UN sanctions against Damascus, had suggested to both Assad's regime and the opposition that they should meet in Moscow for "informal contacts" without any preconditions.
"Our offer has already received a positive response from the Syrian authorities," the foreign ministry said.
But the head of the opposition Syrian National Council said that the opposition rejected all such talks with the Damascus regime until Assad steps down.
"The resignation of Assad is the condition for any negotiation on the transition to a democratic government in Syria," Burhan Ghalioun told AFP.
The Russian foreign ministry had warned the Syrian opposition that Moscow was counting on its participation in the talks.
"We are expecting that the opposition will also give their assent in the next days and put the interests of the Syrian people before any other ideas," it said.
Moscow's diplomatic moves come at a time of mounting concern that the clashes between the opposition and regime forces have become even deadlier with 80 people killed across Syria on Sunday alone, according to activists.
This is on top of what the United Nations said at the start of January already amounted to 5,400 deaths in the standoff.
Russia also appears keen to prove it is playing a constructive role to defuse the crisis, amid mounting Western frustration over Moscow's refusal to support a UN Security Council resolution condemning the Assad regime.
The foreign ministry said that the talks in Moscow were "acutely necessary for the immediate cessation of all violence in Syria and preventing a bloody split in society."
They would also help ensure the "success for profound democratic changes in the country, in line with the hopes of all Syrians."
Russia said its offer to host talks was motivated by its desire to see an end to the crisis "through a peaceful mechanism worked out by the Syrians themselves, without international interference."
Moscow still maintains close ties with the secular regime in Damascus that were cultivated under Assad's father and strongman predecessor Hafez al-Assad and extend to having a naval base in the country and supplying arms.
European and Arab nations on Friday pressed for UN Security Council backing for an Arab League plan calling on Assad to stand down, but Russia said their proposed resolution crossed its "red lines."
Russia has repeatedly condemned the West for what it says is a one-sided approach on Syria and said that both the opposition and the Assad regime are equally to blame for the violence.