The chief negotiator of Syria's main opposition umbrella group, Mohammed Alloush, has resigned over what he called the failure of peace talks.
Mr Alloush, from the High Negotiations Committee (HNC), said the talks had not brought a political deal or eased the plight of Syrians in besieged areas.
The HNC suspended its involvement in the UN-brokered "proximity" negotiations with a Syrian government delegation in Geneva in April.
No date has been set for a resumption.