UNITED NATIONS — U.N. inspectors Monday reported widespread use of chemical weapons in Syria as Britain, France, and the United States launched a push for a tough Security Council resolution on the issue.
The keenly awaited inspectors' report stated that there was clear evidence sarin killed hundreds of people in an August 21 attack that triggered threats of western military strikes against Bashar Assad's regime.
"The conclusion is that chemical weapons have been used in the ongoing conflict between the parties in the Syrian Arab Republic . . . against civilians, including children, on a relatively large scale," said the report, which was to be released later by U.N. Secretary General Ban Ki-moon.
The report said there was "clear and convincing" evidence of the use of sarin gas in the August 21 attack and that surface-to-surface rockets containing the nerve agent were used to deliver it.
The detail was in the first page of the report which was inadvertently leaked when it was included in an official picture of U.N. investigation leader Ake Sellstrom handing over the report to Ban.
Ban was to give the full report to the U.N. Security Council on Monday.
The United States, Britain, and France blame Assad's forces for the attack and say it killed more than 1,400 people. The government, backed by Russia, denies the charge and blames opposition rebels.
The details of the report's contents emerged as the western allies, meeting in Paris, warned Syria of "serious consequences" if it stalls on handing over its chemical weapons.
Kickstarting a week of intense diplomatic activity in the wake of a weekend U.S.-Russia deal on the proposed disarmament, the three powers also moved to bolster rebels fighting Assad's regime and reiterated calls for the Syrian president to step down.
The tough tone triggered an immediate warning from Russia that western saber-rattling could derail efforts to bring the regime and rebels to the table for negotiations aimed at ending a civil war that has raged for over two years and left more than 110,000 people dead.
Secretary of State John Kerry said it was vital that the allies, who came to the brink of launching air strikes against Assad earlier this month, maintain the pressure on the regime.
"If Assad fails to comply with the terms of this framework make no mistake we are all agreed, and that includes Russia, that there will be consequences," Kerry said. "If the Assad regime believes that this is not enforceable and we are not serious, they will play games."
British Foreign Minister William Hague added: "The pressure is on them [the Syrians] to comply with this agreement in full. The world must be prepared to hold them to account if they don't."
The United States and Russia agreed in Geneva on Saturday that an ambitious accord aimed at eliminating Syria's chemical weapons by mid-2014 be enshrined in a Security Council resolution backed up by the threat of unspecified sanctions in the event of non-compliance.
Russia has made it clear it will block any move to write an explicit authorization for the use of military force into the resolution.
Lavrov said that kind of approach would scupper hopes of a resumption of suspended peace negotiations in Geneva.
"If for someone it is more important to constantly threaten . . . that is another path to wrecking completely the chances of calling the Geneva-2 conference," Lavrov told journalists in Moscow.
The U.S.-Russia deal agreed on Saturday gives Assad a week to hand over details of his chemical weapons stockpiles and calls for inspections of what the United States says are some 45 sites linked to the program, which is to be underway by November with the aim of neutralizing the country's chemical capacity by mid-2014.
The deal was greeted with dismay by rebel leaders, who fear that the West's willingness to do business with Assad will consolidate his grip on power and stall the momentum of moves to provide them with the arms they need to tilt the balance of the civil war in their favor.
Fabius and Kerry attempted to reassure the rebels that they had not been forgotten with the French minister announcing an international meeting with leaders of the Syrian National Coalition on the sidelines of the U.N. General Assembly in New York next week.
"We know that in order to negotiate a political solution, there has to be a strong opposition," Fabius said.
France has long championed the opposition coalition but there is concern in other western capitals about the prominent role that hardened Islamist fighters are playing in the fight against Assad's forces.
Kerry also emphasized that Assad's agreement to the chemical weapons handover did not give him any more right to remain in power.
"Nothing in what we've done is meant to offer any notion to Assad . . . that he has some extended period as a leader, so-called," Kerry said.