U.N. Secretary-General Ban Ki-moon said there were serious questions about the sustainability of a Syrian peace plan. An April 12 cease-fire appeared to hold, though violence is reportedly escalating in the country.
The Russian Foreign Ministry said Friday there were "violations and provocations" to the cease-fire and warned the country was headed toward serious crisis if both sides refused to lay down their weapons.
"The issue in Syria now is the choice between a transition toward peaceful, nationwide talks or a descent into civil war," the ministry said in a statement cited by Russia's state-run news agency RIA Novosti.
French President Nicolas Sarkozy, during a Friends of Syria meeting in Paris, accused the government in Damascus of trying to wipe the rebel city of Homs "off the map."
Some governments accuse Damascus of war crimes in its assault on opposition groups inside the country. The Syrian government, however, maintains its fighting a rebellion.
"The shelling of Homs and other cities must end, immediately," U.S. Ambassador to the United Nations Susan Rice said in a statement. "The government must pull back its troops and heavy weapons from the population centers, immediately."
The United Nations estimates that at least 9,000 people were killed in Syria as a result of an uprising that began in March 2011.