BEIRUT, Lebanon -- Syria's top political opposition leader on Wednesday expressed willingness for the first time to talk with representatives of President Bashar al-Assad, softening what had been an absolute refusal to negotiate with the government in an increasingly chaotic civil war.
The opposition leader, Sheik Ahmad Moaz al-Khatib, coupled his offer with two demands: the release of what he described as 160,000 prisoners held by Mr. Assad's government, and the renewal of all expired passports held by Syrians abroad -- a gesture apparently aimed at disaffected expatriates and exiled opposition figures who could not return home even if they wanted to.
Sheik Khatib's offer, published in Arabic on his Facebook page, quickly provoked sharp criticism from others in the Syrian opposition coalition, with some distancing themselves and complaining that the leader had not consulted with colleagues in advance. The sheik later clarified in a second statement that he was expressing his personal opinion, while he chided critics in among his colleagues who he described as "those sitting down on their couches and then saying 'Attack -- don't negotiate.' "
The mutual criticisms reflected the fractiousness that has plagued the Syrian opposition movement since its struggle to depose Mr. Assad began as a peaceful political movement nearly two years ago. Nonetheless, the offer still represented a potential opening for dialogue in the conflict, which has threatened to destabilize the Middle East.
Sheik Khatib made the offer as the United Nations was scrambling to raise money to manage the humanitarian crisis caused by the conflict, which has sent at least 700,000 Syrians into neighboring countries and left more than one million displaced inside Syria. A donor conference under way in Kuwait has produced commitments for about $1 billion of the $1.5 billion that the United Nations is seeking.
"I announce that I am willing to sit down with representatives of the Syrian regime in Cairo or Tunisia or Istanbul," Sheik Khatib said in the offer. His motivation to make such an offer, he said, was "to search for a political resolution to the crisis, and to arrange matters for the transitional phase that could prevent more blood."
There was no immediate Syrian government response to Sheik Khatib, a respected Sunni cleric who once had been the imam of the historic Umayyad mosque in Damascus. His unified Syrian opposition coalition, created at a meeting in Qatar two months ago, has been formally recognized by the Arab League, the European Union and the United States.
Sheik Khatib's offer was made less than a day after the peace envoy for Syria from the United Nations and Arab League, Lakhdar Brahimi, gave the United Nations Security Council a pessimistic prognosis for negotiations.
It also followed a grisly massacre discovered on Tuesday in the contested northern city of Aleppo, from which anti-Assad activists posted videos online of scores of bound victims who had been shot in the head and dumped in a river. Some insurgents said the death toll exceeded 100, mostly abducted men in their 20s and 30s.
Both sides in the conflict blamed the other for those killings, just as they have traded accusations for other atrocities, including two major explosions a few weeks ago that killed more than 80 people at the University of Aleppo. Outside assessments based on video of the university blasts have suggested that a Syrian military missile was responsible.
Sheik Khatib did not hide his contempt for Mr. Assad's government in his statement, saying, "One can't trust a regime that kills children and attacks bakeries and shells universities and destroys Syria's infrastructure and commits massacres against innocents, the last of which won't be the Aleppo massacre, which is unprecedented in its savagery."
But he decided to reach out, he wrote, partly because the Syrian government had publicly invited political opposition leaders this week to return to Damascus for what it called a dialogue.
Three weeks ago, Mr. Assad said in a speech that he was open to reconciliation talks but not with political opponents he described as terrorists, the government's generic term for armed insurgents. At the time, most members of the political opposition dismissed Mr. Assad's speech as meaningless.
The opposition's longstanding position has been that Mr. Assad must resign as a precondition for any talks and that he cannot be part of any transitional government. Mr. Assad and his aides have said he has no intention of resigning and may even run for another term in elections next year.
Hania Mourtada reported from Beirut, and Rick Gladstone from New York. Reporting was contributed by Anne Barnard and Hwaida Saad from Beirut.
This article originally appeared in The New York Times.