The rebel Free Syrian Army says it is no longer bound by a United Nations-backed cease-fire agreement as international efforts to end the bloody conflict were set to ramp up with renewed diplomacy later this week.
Rebel spokesman Sami al-Kurdi told the Reuters news agency Monday the FSA had "decided to end our commitment to this [plan]" and have only resumed offensive operations "to defend our people."
The Britain-based Syrian Observatory for Human Rights said at least 80 government soldiers were killed over the last few days as rebels intensified attacks on government checkpoints. Syrian state media have not acknowledged the casualties and there is no independent confirmation.
International mediator Kofi Annan is due to brief the U.N. Security Council Thursday in New York and U.S. Secretary of State Hillary Clinton Friday in Washington. On Monday, Annan urged major powers to ensure his peace plan was implemented by both sides as it remains "the only option on the table."
Russia has blunted Western efforts to condemn Syrian President Bashar al-Assad and push him from power.
A European Union summit with Russian President Vladimir Putin failed to resolve differences in how to deal with Syria's 15-month long conflict. Speaking at the St. Petersburg summit, European Council President Herman Van Rompuy said the Russian leader and the 27-nation bloc have "some divergent assessments" about Syria.
Van Rompuy said both sides need to work together to achieve an immediate halt to Syria's violence and launch a process of political transition in the country, led for 11 years by Mr. Assad.
"On Syria, let me say that the situation is appalling," said Van Rompuy. "The Syrian regime should immediately cease all forms of violence and provide its full support to the U.N. supervision mission. The European Union and Russia might have some divergent assessments but we fully agree that [U.N. and Arab League envoy Kofi] Annan's plan as a whole provides the best opportunity to break the cycle of violence in Syria, avoiding the civil war and finding a peaceful lasting solution. We need to combine our efforts in order for this to happen and to find common messages on which we agree.''
Russia and the West have long disagreed about which side of the Syrian conflict should do more to end the violence. Moscow says Mr. Assad and the rebels trying to oust him have an equal obligation to stop fighting, while Western powers say the Syrian president should act first by ending his deadly crackdown on dissent.
Also Monday, White House spokesman Jay Carney said Assad was lying when he denied his government had massacred 108 civilians, mostly women and children, in the Houla area of Homs province on May 25. Asked if Mr. Assad was "lying again to the world," Carney said "yes."
In New York, China's U.N. ambassador, Li Baodong, said his government is not attempting to protect Mr. Assad and will respect the will of the Syrian people on the country's future. He acknowledged the impact of the Houla massacre on diplomatic efforts to curb the killing in Syria.
"What happened in Houla [is definitely] a setback for efforts to solve the crisis in Syria and has caused colossal damage to Kofi Annan's mediation efforts," said Li Baodong.
Li, the Security Council president this month, warned that if Mr. Annan's peace plan isn't quickly enacted, violence in Syria would turn into "full-fledged civil war" that may spill over and affect Mideast peace.