DEVELOPMENTS

•President Vladimir Putin said Tuesday that Russia has not yet fulfilled a contract to send sophisticated S-300 air defense missile systems to Syria to avoid tilting the balance of power in the region. Russian officials have acknowledged that Moscow signed a deal for the delivery of the powerful missiles a few years ago, but have been coy about whether any of them have been delivered. Putin also criticized the EU’s decision to lift its weapons embargo for Syrian rebels, saying that Russia was “disappointed” by the move, which he said ran contrary to international law. He said Russia would continue to push for a peace conference on Syria, but added that the prospects for convening it have been clouded by the “lack of goodwill on behalf of the armed opposition.”

• Syrian troops advanced toward the center of the strategic town of Qusair near the border with Lebanon and chased rebels from another key district on the edge of Damascus on Tuesday, officials said, solidifying gains that have shifted the balance of power in the regime’s favor in recent weeks. In the past two months, the Syrian army has moved steadily against rebels in key battleground areas, making advances near the border with Lebanon and considerably lowering the threat to Damascus, the seat of President Bashar Assad’s government.

Associated Press

France said Tuesday it has confirmed that sarin gas was used “multiple times and in a localized way” in Syria, including at least once by the regime, making the most specific claim yet by any Western power about chemical weapons attacks in the 27-month-old conflict.

Britain later said that tests it conducted on samples taken from Syria also were positive for sarin.

The back-to-back announcements left many questions unanswered, highlighting the difficulties of confirming from a distance whether combatants in Syria have crossed the “red line” set by President Barack Obama. The regime of Syrian President Bashar Assad has refused to allow U.N. investigators into the country.

The French and British findings came hours after a U.N. team said it had “reasonable grounds” to suspect small-scale use of toxic chemicals in at least four attacks in March and April.

The U.N. probe was conducted from outside Syria’s borders, based on interviews with doctors and witnesses of purported attacks and a review of amateur videos from Syria. The team said solid evidence will remain elusive until inspectors can collect samples from victims directly or from the sites of alleged attacks.

n the West, meanwhile, the lack of certainty about such allegations is linked to a high stakes political debate over whether the U.S. should get more involved in the Syria conflict, including by arming those fighting Assad.

Obama has been reluctant to send weapons to the rebels, in part because of the strong presence of Islamic militants among them. Obama has warned that the use of chemical weapons or their transfer to a terrorist group would cross a “red line,” hinting at forceful intervention in such an event.

Yet he has insisted on a high level of proof, including a “chain of custody,” that can come only from on-site investigations.

In Tuesday’s announcement about sarin, French Foreign Minister Laurent Fabius said his government had analyzed several samples, including some brought back by reporters with Le Monde newspaper.

He said there was “no doubt” that in at least one case, the regime and its allies were responsible for the attack. “We have integrally traced the chain from the attack to the moment people were killed, to when the samples were taken and analyzed,” Fabius said.

He said a line was crossed and that “all options are on the table,” including intervening “militarily where the gas is produced or stored.”

White House spokesman Jay Carney said the French report is “entirely consistent” with the Obama administration’s own findings, but added more work needs to be done to establish who is responsible for the use of the toxic substances and when they were used. “We need more information,” he said.

Russia, meanwhile, has rejected intelligence the U.S. provided last month suggesting the Assad regime used chemical weapons on its own people, American officials said. A U.S. diplomatic delegation that was sent to Moscow failed to persuade Russian officials and prompted no change in the Kremlin’s support for Assad.

Experts, meanwhile, disagreed on whether the latest chemical weapons allegations mean Obama’s red line has been crossed.

“The verdict is still open,” said Jean Pascal Zanders, an independent chemical weapons consultant, speaking before the French announcement.

Zanders said that while claims of chemical weapons use cannot be ignored, the details of the alleged attacks often don’t correspond to the purported symptoms shown in videos or reported by witnesses.

Analyst Michael Eisenstadt said he believes Obama’s red line “has indeed been crossed on a number of times, as there are persistent reports of limited, continued use of chemical weapons from various sources that seem fairly credible.”