British scientists have found positive evidence of deadly sarin gas on samples of cloth and soil from the Damascus suburb believed to have been targeted by forces loyal to Syrian president Bashar Assad.
The UK's confirmation of poison gas use will further fuel calls for action against Assad at the G20 summit, where host Vladimir Putin has agreed to put Syria on the agenda for talks over dinner tonight.
Deputy Political Editor Chris Ship reports from St Petersburg:
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.