Russia has called for the swift adoption of a Security Council resolution to send hundreds of observers to monitor the shaky ceasefire.

"We should do everything we can to adopt, as soon as possible, a second resolution that will approve a full-scale observer mission," Foreign Minister Sergei Lavrov said. 

Lavrov said global and regional powers should "apply pressure to all groups in Syria without exception" to cooperate in implementing Annan's plan, which includes calls for a ceasefire, withdrawals and political dialogue.

Lavrov reiterated Russia's claim that some foreign nations hope Annan's plan will fail, paving the way for other forms of pressure on Assad's government, potentially ranging from sanctions to military intervention.

"There are some, including outside Syria, who would like to spoil Annan's plan," he said.