US Secretary of State John Kerry said "anything less than full compliance from the Assad regime" on the chemical weapons handover would not be tolerated.
He added: "If Assad fails to comply with the terms of this framework, make no mistake, we are all agreed, and that includes Russia, that there will be consequences."
Kerry later added that Assad's government had "lost all legitimacy."
While the UN confirmed that sarin was used in a chemical weapons attack, conventional weapons are still destroying families in Syria.
The UN Secretary General has said there is "overwhelming and indisputable" evidence that chemical weapons were used in an attack in Syria.