BEIRUT, Lebanon — Syrian government forces and their allies in Hezbollah, the Lebanese militant group, seized most of the strategic crossroads town of Qusayr early on Wednesday, a painful defeat for outgunned Syria rebels and an advance for President Bashar al-Assad. If it sticks, the military gain could infuse his forces with momentum and embolden him to push for military victory just as Russia and the United States are pressing the combatants to negotiate.
By ANNE BARNARD The New York Times
The government’s triumphal advance into Qusayr also suggested that the intervention on Mr. Assad’s side by Hezbollah had proved decisive as its fighters besieged, then stormed, a rebel stronghold that the Syrian military had bombarded in vain for months.
But the intervention also carries big political risks for Hezbollah, which has historically been revered in Syria for its opposition to Israel but is now seen as a sectarian-driven occupying force by Mr. Assad’s insurgent enemies, who are mostly Sunni. Hezbollah has said it intervened in Syria to protect neighboring Lebanon from Islamist extremists.
The government claimed victory in Qusayr, broadcasting pictures of soldiers raising flags over wrecked buildings as the rebels said they had withdrawn from much of the town. Mr. Assad also received congratulatory messages from his most important regional ally, Iran, which regards Syria as a vital partner.
At the same time, senior American, Russian and United Nations officials convened in Geneva to try to find enough common ground among themselves and the Syrian combatants to hold talks to halt the carnage and work toward a political transition.
By late afternoon, the sides had failed to agree even on who would attend the conference, and officials said they would adjourn and try again on June 25. Lakhdar Brahimi, the special United Nations representative on Syria, told reporters that “evidently, there is still a lot of work to do.”
With the Syrian opposition’s political leaders disunited and the government defiant, expectations remained low for any talks aimed at halting the conflict, which is more than two years old and has left an estimated 80,000 people dead.
The Geneva meeting was also overshadowed by statements from France and Britain over the past day that sarin nerve gas had been used in Syria. The statements confronted American officials with the possibility that Mr. Assad’s government had crossed what President Obama has called a “red line” that could prompt American intervention — an option for which the administration has shown waning enthusiasm. However, a cabinet shuffle on Wednesday appeared to give new prominence to advocates of a more active American role, if not of direct military intervention.
A day after France announced that French laboratory tests had confirmed that sarin gas had been used “multiple times” in Syria “in a localized way,” Britain on Wednesday repeated an earlier assessment that “a growing body of limited but persuasive information” pointed to the use of the same toxin.
French and British officials did not make public the details of the evidence on which their assessments were based. The French statements said there was “no doubt” the government or its accomplices were behind the alleged use of the gas in at least one case, based on samples of bodily fluids from victims, including urine samples brought out of Syria by French journalists. British statements were more cautious, saying “the room for doubt” about the use of sarin “continues to diminish” and that the use was “very likely” by the government.
In Qusayr, further underscoring the volatility of the conflict, rebels and anti-government activists said their fighters would battle on in surrounding villages and in the northern part of the town, where they are most deeply entrenched. Syria state media acknowledged that the fight was not completely over, saying the military was still sweeping northern Qusayr for militants.
Reporting was contributed by Hwaida Saad and Hania Mourtada from Beirut; Nick Cumming-Bruce from Geneva; an employee of The New York Times from Daba’a, Syria; Alan Cowell from London; Steven Erlanger from Paris; and Rick Gladstone from New York.