Syria is believed to have the Arab world's largest stockpile of chemical weapons. An ex-official warned that Assad would use them if backed into a corner.
Fighting has intensified in the capital, a day after the Red Cross declared the conflict a 'civil war' and reminded combatants of the rules of war.
Rapid deterioration of the situation in Syria has given world leaders a sense of urgency, but they seem no closer to finding common ground.
Whatever restraint that was being exercised by the parties to Syria's civil war appears to have been cast aside.