The head of the UN's observer mission to Syria has acknowledged "some frustrations" at the failure to reduce violence and end the Syrian government's use of heavy weapons against its people, as the monitors are set to leave the country.
The UN observers' departure comes after the Security Council agreed to end the mission and back a small new liaison office that will support any future peace efforts.
The expiry of the observers' mandate represents a serious blow to international efforts to end the conflict.
Al Jazeera's Scott Heidler looks at what the UN mission achieved and what future role the organisation can play.
