The special UN-Arab League envoy for Syria, Kofi Annan, holds talks in Moscow today with President Dmitry Medvedev.
Annan is seeking Russian backing for his efforts to secure a cease-fire.
On the eve of the talks, the Kremlin said it would be hard to enforce a halt to the violence "until external armed and political support of the opposition is terminated."
Moscow has accused the West of being too one-sided in the conflict, arguing that outside support for rebels is fueling the fighting in Syria, home to a Russian naval base.
Annan has warned the conflict in Syria could spread to neighboring countries and urged world powers to unite behind his efforts.
Meanwhile, Syrian forces are reported to have fired on the battered city of Homs and other rebel strongholds, with at least 24 reported killed.
Also, the European Union added two state-owned oil companies - Syrian Petroleum Company and Mahrukat Company - to its list of organizations facing sanctions, a day after it banned Assad's wife from traveling to the EU.
Based on reporting from Reuters