A diplomatic breakthrough on securing and destroying Syria's chemical weapons stockpile has averted the immediate threat of US military action and could swing momentum towards ending a horrific civil war.
Marathon negotiations between US and Russian diplomats at a Geneva hotel produced a sweeping agreement that will require one of the most ambitious arms-control efforts in history.
The deal involves making an inventory and seizing all components of Syria's chemical weapons programme and imposing penalties if President Bashar Assad's government fails to comply with the terms.
After days of intense day-and-night negotiations between US secretary of state John Kerry and Russian foreign minister Sergey Lavrov and their teams, the two powers announced they had a framework for ridding the world of Syria's chemical weapons.
The US says Assad used chemical weapons in an August 21 attack on the outskirts of the capital Damascus, killing more than 1,400 civilians. That prompted President Barack Obama to ready American air strikes on his order - until he decided last weekend to ask for authorisation from the US Congress. Then came the Russian proposal and Mr Obama asked congress, already largely opposed to military intervention, to delay a vote.
Mr Obama said the deal "represents an important, concrete step toward the goal of moving Syria's chemical weapons under international control so that they may ultimately be destroyed". "This framework provides the opportunity for the elimination of Syrian chemical weapons in a transparent, expeditious and verifiable manner, which could end the threat these weapons pose not only to the Syrian people but to the region and the world," he said.
Mr Kerry and Mr Lavrov said they agreed on the size of the chemical weapons inventory and on a speedy timetable and measures for Assad to do away with the toxic agents. But Syria, a Moscow ally, kept silent on the development, while Mr Obama made it clear that "if diplomacy fails, the United States remains prepared to act".
The deal offers the potential for reviving international peace talks to end a civil war that has claimed more than 100,000 lives and sent two million refugees fleeing for safety, and now threatens the stability of the entire Middle East.
Mr Kerry and Mr Lavrov, along with the United Nations-Arab League envoy to Syria, Lakhdar Brahimi, said the chances for a follow-up peace conference in Geneva, Switzerland, to the one held last June would depend largely on the weapons deal.
The US and Russia are giving Syria just one week, until September 21, to submit "a comprehensive listing, including names, types and quantities of its chemical weapons agents, types of munitions, and location and form of storage, production, and research and development facilities". International inspectors are to be on the ground in Syria by November. During that month, they are to complete their initial assessment and all mixing and filling equipment for chemical weapons is to be destroyed. They must be given "immediate and unfettered" access to inspect all sites. All components of the chemical weapons programme are to be removed from the country or destroyed by mid-2014.