A briefing to the UN Security Council on behalf of international mediator Kofi Annan has offered a pessimistic outlook, according to diplomats. Opinion remains split on the best way to end the violence.
The council was briefed by Annan's deputy, Jean-Marie Guehenno, who was speaking from Geneva via videophone.
Guehenno told the assembly that Syrian protesters "have lost fear and are unlikely to stop their movement," one diplomat said.
Officials also claimed that Guehenno had highlighted doubts to the closed session that Syrian President Bashar al-Assad had any intention of honoring a six-point peace plan.
The report follows the visit of Arab League and UN mediator Annan's visit to Damascus, where he met Assad. At the meeting, Annan is believed to have urged Assad to adhere to principles of the cease-fire plan.
Confused picture of massacre
The Syrian government was widely criticized after at least 108 people were killed in a two-day offensive near the town of Houla. Some 49 children and 34 women were among those who died. The true identities and allegiances of the perpetrators have yet to be established, but UN monitors have said there is evidence that contradicts Syrian government denials that armed forces and allied militia were responsible.
At the Security Council meeting, Germany's UN ambassador Peter Wittig said the body should be capable of making the parties responsible for civilian deaths accountable.
"We think the last 15 months have shown that inaction of the council leads to this vicious circle of violence," Wittig told reporters. "We need to overcome that - and hopefully today's debate will make a contribution."
There was further outrage on Wednesday as UN observers said 13 bodies had been found in eastern Syria. The victims were shot in the head.
French President Francois Hollande said on Tuesday that military intervention was an option that could be considered.
'No reason to think militarily'
But Germany appears to be at odds with its NATO ally, saying there were no grounds to even debate military action.
"From the federal government's point of view, there is no reason to speculate over military options," Foreign Minister Guido Westerwelle was quoted as saying in the daily newspaper Die Welt.
However, Westerwelle did urge those "who have hesitated to withdraw their support" for Syria to decisively isolate Damascus, using "all political leverage" to end to the bloodshed.
Earlier on Wednesday, Russia's Deputy Foreign Minister Gennady Gatilov told the Interfax news agency that it was too early for the Security Council to take new action in the wake of the killing of 108 people in Houla.
Meanwhile, Chinese Foreign Ministry spokesman Liu Weimin told reporters that China remained opposed to military intervention.
rc/ncy (AP, AFP, dpa, Reuters)