"We believe there was progress made this round towards the base or the need for a base of a single opposition delegation to participate in negotiations with the government of Syria," de Mistura told reporters.
De Mistura also said he received a proposal of the Syrian government delegation at the Geneva talks to exchange the detainees and abducted people.
"We heard an interesting suggestion by the delegation of the government regarding concrete possibility of the exchanges of detainees and abducted people and obviously the place for doing that is Astana,"he said.
The envoy added that the fifth round of the intra-Syrian talks in Geneva will most likely take place later in March.
“On the basis of the indications that I will be getting both from the Secretary General [UN] and the Security Council, I am planning to invite the Syrian invitees back here in March for a fifth round,” he said.
The fourth round of UN-backed intra-Syrian talks between the government and opposition factions kicked off in Geneva last week and concluded on Friday.