International peace envoy Lakhdar Brahimi said on Wednesday that the Syrian government had agreed to abide by a temporary ceasefire over a four-day Muslim holiday which starts on Friday, DPA reported.
"If this modest initiative succeeds, we hope we can build on it for a longer ceasefire to be part of an integrated political process," Brahimi said in Cairo.
The Syrian opposition cast doubt on whether the government would implement the ceasefire after a Foreign Ministry spokesman said a final decision on the truce proposal would be made on Thursday.
"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 implementing a ceasefire over Eid al-Adha.
The rebel Free Syrian Army said it would reciprocate any government abidance by the ceasefire.
Brahimi met Syrian President Bashar al-Assad on Sunday during a five-day visit to Damascus to try to broker a temporary ceasefire between government forces and the rebels.
Brahimi will on Wednesday brief the UN Security Council on the outcome of his talks in Syria and neighbouring countries.
He will address the 15-member Security Council by a video link from Cairo, said UN spokesman Martin Nesirky.
"Mr Brahimi is pushing extremely hard, as is the Secretary-General, because this is an extremely important moment," Nesirky told reporters in New York.
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.
On the ground, 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, activists said.
The Syrian state news agency blamed what it called "terrorists" for killing at least nine men, three children and one woman in the town.
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.