The Syrian government, however, did not confirm Wednesday's announcement by Lakhdar Brahimi, saying only that it was still studying the envoy's proposal.
Brahimi told reporters in Cairo that President Bashar Assad's government has agreed to a truce for the Eid al-Adha holiday. Brahimi said Damascus will issue a statement on accepting the cease-fire later "today or tomorrow."
The announcement came as government forces intensified airstrikes on a rebel-held area near the besieged city of Aleppo. The fighting in Syria has killed more than 34,000 people since March last year, according to activists.
Brahimi did not elaborate on how the truce would be monitored. The envoy has met with Assad in Damascus on Sunday as part of his push for a cease-fire between rebels and government forces. He also held talks last week with opposition groups inside and outside Syria and earlier received "promises" but not a "commitment" from them to honor the cease-fire.
In Damascus, Foreign Ministry spokesman Jihad Makdessi stressed Wednesday that the cessation of military operations during Eid al-Adha is still "being studied" by the General Command of the Army and the Syrian armed forces, and that "the final position on this matter will be issued on Thursday."
Abdelbaset Sieda, the head of the Syrian National Council, the main opposition group in exile, told The Associated Press that he had little hope the truce would take hold. He 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," Sieda said in a phone interview from Stockholm, Sweden.
Brahimi's proposal is far more modest than a six-point plan by his predecessor as Syrian envoy, former U.N. Secretary General Kofi Annan. A cease-fire was the centerpiece of Annan's proposal and was to lead to talks on a peaceful transition.
However, a truce never took hold and both sides violated their commitments, though Annan said at the time the regime was the main aggressor because it refused to withdraw troops and heavy weapons from population centers.
In Syria, regime warplanes struck the village of Mar Shureen near a strategic rebel-held town in the country's north Wednesday, killing five members of an extended family, activists said.
The village is located just outside the town of Maaret al-Numan, about a mile (1.5 kilometer) from a Syrian military camp that troops and rebels have been fighting over for several days.
Rami Abdul-Rahman, the director of the Britain-based Syrian Observatory for Human Rights told The AP that government aircraft hit the village in the morning hours. The dead include a father and his two sons, aged 10 and 24, as well as a two other relatives, a woman and a young man, Abdul-Rahman said. His group relies on reports from a network of activists on the ground.
Opposition fighters seized Maaret al-Numan, which lies along the main highway between Aleppo and Damascus, earlier this month, disrupting the ability of Assad's army to send supplies and reinforcements to the northwest where troops are bogged down in a stalemate with the rebels in Aleppo, Syria's largest city.
At least 10 people were killed and 13 were injured when an artillery shell landed near a bakery in Aleppo, Abdul-Rahman said.
Amateur video posted Tuesday showed stacks of pita bread on shelves, soaked in blood, and human remains scattered on the floor. Residents are also seen carrying injured people, some missing limbs, out of a shop that appears to be a bakery, loading them into civilian cars as a man shouts: "May God punish you, Bashar ... He is bombing the people at the bakery. "
Syria restricts access to foreign reporters and the authenticity of the video could not be independently confirmed.
Associated Press writers Maggie Fick in Cairo, Karin Laub in Beirut and Albert Aji in Damascus contributed to this report.