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The current international peace plan seeking to stop Syria's civil war suffered a major setback Wednesday when an al-Qaida-inspired militant group rejected a cease-fire proposed by the international envoy.

Lakhdar Brahimi, the U.N.-Arab League envoy for Syria, said the government in Damascus and some rebel leaders had agreed to a four-day truce during the Muslim Eid al-Adha holiday, which starts Friday.

The modest scope of the proposal reflected how short the international community is on ideas — and even that appeared doomed. Both sides have agreed to previous, more ambitious cease-fires in the past only to break them, and neither side shows much interest in stopping the fight now.

The Syrian government denied it has made a decision, saying it is studying the proposal, and rebel leaders have expressed doubts.

An extremist group, Jabhat al-Nusra, which has joined the fight against President Bashar Assad, also 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."

While the group is on the extreme edge of the rebel groups fighting in Syria, it also expressed a sentiment most of them share: that after 19 months of deadly violence, there is little faith that Assad's regime will abide by any agreement.

Brahimi told reporters in Cairo Wednesday that Assad's government had agreed to the truce and would issue a statement on the matter later "today or tomorrow." He did not say how it would be monitored.

Brahimi met with Assad in Damascus on Sunday after talks last week with opposition groups inside and outside Syria. He has said he received promises but not a commitment from them to honor the cease-fire.

Speaking by videoconference from Cairo on Wednesday, he told the U.N. Security Council that he hopes a temporary cease-fire in Syria can break the cycle of violence and allow a political transition to start, a U.N. diplomat in the closed meeting said.

He also said another failure would let the conflict worsen and spill over to other countries, the diplomat said, speaking on condition of anonymity because the meeting was private.

In Damascus, Foreign Ministry spokesman Jihad Makdessi said Wednesday that proposal was still "being studied" by Syrian army leaders and that Syria's decision would be announced Thursday.

Another opposition leader said he had little hope the truce would hold. Abdelbaset Sieda, 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," Sieda said by phone from 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.

But the truce broke down soon after it started and the two sides returned to all-out war, although Annan said the regime was the main aggressor.

Violence continued around Syria Wednesday. A car bomb exploded in the Tadamon neighborhood of Damascus, killing at least eight people, said Rami Abdul-Rahman of the Britain-based Syrian Observatory for Human Rights.

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 just outside the town of Maaret al-Numan, about a mile (nearly two kilometers) from a Syrian military camp that has been the site of fierce fighting for several days.

Opposition fighters seized Maaret al-Numan, which lies along the main highway between Aleppo and Damascus, earlier this month. That has disrupted 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.

Syria's uprising started in March 2011 with anti-regime protests. The conflict has since turned into a civil war. Anti-regime activists say more than 34,000 have been killed.

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Associated Press writers Maggie Fick in Cairo, Karin Laub in Beirut and Albert Aji in Damascus contributed to this report.