The UN Security Council on Wednesday called on the Syrian government and opposition groups to accept UN envoy Lakhdar Brahimi's appeal for a ceasefire during the upcoming Muslim holiday of Eid al-Adha, DPA reported.
The council, in a statement, called on all sides, in particular the Syrian government "as the stronger party," to agree to Brahimi's initiative.
"All sides must work toward a sustainable cessation of all violence," the statement said.
Brahimi told the council earlier in a closed meeting via a video link from Cairo that Syrian President Bashar al-Assad had agreed to his proposal. The Syrian government has said it will release a statement with its final position on Thursday.
An Islamist hardline Syrian opposition group called the al-Nusra Front rejected Wednesday the truce, set to coincide with this week's Eid al-Adha festival, which starts Friday.
"There is no truce between us and this regime which is shedding the blood of Muslims," the group said in a statement posted on the internet.
"We will not allow those who give a chance to plotters to trick us," said the group, which has claimed suicide bombings inside the capital Damascus in the past few months and is battling alongside the opposition Syrian Free Army in the northern province of Aleppo.
Brahimi, said the truce was a "small step" towards reaching a settlement to the crisis, adding he was "uncertain" if it would hold.
He called on the council to back his efforts, warning that failure would exacerbate the 20-month conflict in Syria.
Details of the council's meeting, which was held behind closed doors in New York, were reported by diplomats who attended.
"We hope the Security Council can send out a strong signal and can rally behind Brahimi," Germany's UN envoy, Peter Wittig was quoted as saying.
In Washington, US Secretary of State Hillary Rodham Clinton welcomed the possibility, telling reporters: "We have been in close touch with (Brahimi) and his team. We support his call for a ceasefire for the Eid al-Adha holiday so that Syrians could, you know, celebrate in peace."
Other elements of the Syrian opposition reacted with scepticism to Brahimi's announcement.
"As soon as Brahimi gave his statement, a Syrian official said the decision has not been taken yet. This proves that the Syrian regime is not serious," said George Sabra, spokesman for the Syrian National Council, the main opposition group.
"We don't trust this regime because it says something and does something else on the ground," Sabra told dpa.
Brahimi said most opposition leaders whom he had met approved his proposal for the ceasefire.
The rebel Free Syrian Army said it would reciprocate any government adherence to the ceasefire.
Brahimi met al-Assad on Sunday during a five-day visit to Damascus to try to broker a temporary ceasefire between government forces and the rebels.
Kofi Annan, Brahimi's predecessor, quit his mission in August, blaming divisions at the UN Security Council, and the Syrian government for failing to implement a ceasefire.
Meanwhile, in Syria, a car bomb exploded at a military checkpoint in southern Damascus, killing at least six people and wounding 20 others, Syrian state television.
The opposition Syrian Observatory for Human Rights said the blast took place in the Tadamon neighbourhood and targeted a minibus.
Syrian troops intensified attacks in the northern province of Idlib to regain control of a strategic town seized by rebels a week ago, said activists.
Warplanes struck the village of Mar Shuraan in Idlib, killing five members of the same family, they added.
Elsewhere, government forces killed at least 20 people in the pro-rebel town of Douma on the outskirts of Damascus, according to activists.
The Syrian state news agency blamed what it called "terrorists" for killing at least nine men, three children and one woman in the town.
At least 150 people were killed in Syria on Wednesday, according to the London-based Syrian Observatory for Human Rights.
News from Syria cannot be independently verified, as authorities have barred most foreign media from the country since the uprising against al-Assad's rule started in March last year.