The Syrian government has agreed to allow UN inspectors to visit the site of a suspected chemical weapon attack outside Damascus, state media report.
The move came shortly after a senior US official told reporters there was "very little doubt" that a chemical weapon had been used by government forces.
Activists say Syrian forces killed more than 300 people in several suburbs east and west of the capital on Wednesday.
The Syrian authorities have denied any responsibility and blamed "terrorists".
On Saturday evening, US President Barack Obama and UK Prime Minister David Cameron agreed that there should be a "serious response" if Syrian troops had used chemical weapons.
But Syria's information minister warned that US military intervention would bring chaos and that the Middle East would "burn".
Omran Zoabi told Lebanon-based al-Mayadeen TV the Syrian state and its armed forces remained strong, with friends and allies in the region.