Peace envoy Lakhdar Brahimi said yesterday that Syria and "most" rebel factions have agreed to a truce over Eid Al Adha but a top opposition leader said that they "don't trust the regime".
Mr Brahimi, the joint UN-Arab League special envoy, had crisscrossed the Middle East to push the warring factions and their international backers to agree to a truce during the holiday, which starts tomorrow.
"After the visit I made to Damascus, there is agreement from the Syrian government for a ceasefire during the Eid," Mr Brahimi told a news conference at the Arab League in Cairo.
While Syria's president Bashar Al Assad was said to have agreed to Mr Brahimi's deal, the Syrian foreign ministry said yesterday that the military command was still studying the proposal, but was expected to confirm the ceasefire today.
But the modest scope of the proposal reflected how short the international community is on ideas.
Abdulbaset Saida, the head of the exile Syrian National Council, said opposition fighters have told him they are willing to adhere to it but will respond if attacked by regime forces.
"This regime, we don't trust it, because it is saying something and doing something else on the ground," Mr Saida said.
At least one rebel group, the Islamists Jabhat Al Nusra, rejected the truce.
"There will be no truce between us and the prideful regime and shedder of the blood of Muslims," the group said in a written statement posted Wednesday on militant websites. "We are not among those who allow the wily to trick us, nor are we ones who will accept to play these filthy games."
The UN Security Council backed the ceasefire between the warring sides in Syria and urged neighbouring countries to "use their influence" to push for an end to the war.
A previous ceasefire arrangement in April collapsed within days, with both sides accusing the other of breaking it.
On the way into the council meeting, Russia's UN Ambassador Vitaly Churkin said Moscow hoped Mr Brahimi's plan would be successful.
"We support it very strongly," Mr Churkin said. "We worked very hard in support of Mr Brahimi in making sure there is a chance that might happen."
Also yesterday, Russia's chief military officer said Syrian rebels had acquired portable air defence missiles, including US-made Stinger missiles.
Gen Nikolai Makarov, the chief of the military's General Staff, did not say how many such missiles the rebels had and who supplied them.
In remarks carried by Russian news agencies, Gen Makarov alleged that some of the weapons could have been delivered by commercial airlines.
The violence continued in Syria yesterday as a car bomb killed several people in the capital. State television blamed the explosion on "terrorists" and said there were six fatalities while the Syrian Observatory for Human Rights put the number at eight. They agreed that 20 people were wounded in the blast.
The Observatory added that unidentified attackers blew up a Syrian gas pipeline in the eastern province of Hasakeh.
It also reported that five people from one family, including a child and a woman, were killed in government air strikes on the northern town of Maarat Al Numan.
Opposition fighters seized Maaret Al Numan, which lies along the main motorway between Aleppo and Damascus, earlier this month. That has disrupted the ability of Mr Al Assad's army to send supplies and reinforcements to the north-west where troops are bogged down in a stalemate with the rebels in Aleppo, Syria's largest city.
Opposition activists and Syrian state media traded blame for the killing of at least 25 people, including women and children, in the town of Douma near Damascus.
"People now are scared and very angry. Some of the martyrs were killed with knives, others were shot," Mahmoud Doumany, an activist living in Douma, said.
Syrian state television said 25 people had been killed by "terrorist members of the so-called 'Liwa Al-Islam.'"
Hundreds of Syrian refugees have poured into a makeshift refugee camp at Atimah overlooking the Turkish border, fleeing a week of what they said were the most intense army bombardments since the uprising began.
"Some of the bombs were so big they sucked in the air and everything crashes down, even four-storey buildings. We used to have one or two rockets a day, now for the past 10 days it has become constant, we run from one shelter to another. They drop a few bombs and it's like a massacre," said one refugee, a 20-year-old named Nabil.
US Secretary of State Hillary Clinton warned yesterday that Syria would exploit any power vacuum in Lebanon, worsening tensions in the Middle East after a deadly bomb blast in Beirut.
"We don't want to see a vacuum of legitimate political authority that could then be taken advantage of by the Syrians or by others that could create even greater instability and violence," Ms Clinton told a news conference.
Her comments came as a high-ranking member of the Lebanese president Michel Suleiman's office revealed that he "has begun consultations with the leading figures of the country, in the context of the national dialogue, to discuss the possibility of forming a new government."
Lebanon has been in crisis since Friday, when police intelligence chief Gen Wissam Al Hassan was killed in a Beirut car bombing blamed on Damascus, leading opposition leaders to demand Prime Minister Najib Mikati's resignation.
* With reporting by Reuters, Agence France-Presse and Associated Press