The chief peace negotiator of Syria's mainstream opposition said Sunday he is resigning over the failure of the U.N.- backed Geneva peace talks to bring a political settlement and to ease the plight of Syrians living in besieged rebel-held areas.

Mohammed Alloush, who is also the representative of the powerful Jaish al-Islam rebel faction in the Saudi-based High Negotiations Committee (HNC), said in a statement that the peace talks have also failed to secure the release of thousands of detainees or to push Syria toward a political transition without President Bashar Assad.

The U.N.-backed parties have not set a date for the resumption of the peace talks after the HNC suspended their participation until the situation on the ground has radically changed.