New Delhi: UN Syria envoy Staffan de Mistura has said expressed his hope to launch "real, substantive" peace talks in October.

De Mistura has previously hosted seven rounds of largely unsuccessful talks, with the fate of President Bashar al-Assad standing out as a main obstacle to progress. 

The United Nations envoy wants to see the Saudi-backed opposition High Negotiations Committee (HNC) -- which has insisted on Assad's ouster -- unite with two more moderate opposition camps, who have a softer line on the Syrian president's future. 

The opposition "does require more time in order to come up (with) a more inclusive and perhaps even a more pragmatic approach," de Mistura said.  

Discussions among the opposition factions are ongoing, but there may be a key meeting in the coming weeks where the sides formally reorganise their delegation ahead of face-to- face talks with the Syrian government, de Mistura said. 

He said that there is "major opportunity for the opposition to take stock of the realities on the ground (and) take stock of their own need to be unified."