President Assad barely dented his stockpile of chemical weapons in an attack last month, the US ambassador to the United Nations claimed.
Samantha Power said: "We assess that although Assad used more chemical weapons on August 21 than he had before, he has barely put a dent in his enormous stockpile."
The G20 summit in St Petersburg exposed stark divisions between host Vladimir Putin and US President Obama over Syria.
War emptied the suburb of Yarmouk in southern Damascus of its people. Assad's army holds it, but their prize is a ghost town.
Even in the President's heartland of Baltimore, 95% of voters are against his policy on military intervention in Syria.