UN eyes October for 'real' Syria peace talks: envoy
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 UN 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 told reporters in Geneva.
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 added 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."
|The�Saudi-backed HNC has long insisted political transition means the departure of Assad.|
An HNC official confirmed the internal opposition talks and said one of the moderate factions, known as the Cairo Platform, was due in the Saudi capital this week for further discussions.
However the Saudi-backed HNC has long insisted political transition means the departure of Assad.
With the rebel fighting position weakened, experts say the regime faces no pressure to make concessions at the negotiating table, and especially not over the question of Assad's future.
De Mistura said he may still try to organise another "preparatory" round of talks in Geneva next month, as initially planned, but stressed that his office "will be focusing on the real agenda for the real substantive talks that we hope will be taking place in October".
The Syrian conflict began when the Baath regime, in power since 1963 and led by Assad, responded with military force to peaceful protests demanding democratic reforms during the Arab Spring wave of uprisings.
It triggered an armed rebellion fuelled by mass defections from the Syrian army.
According to independent monitors, hundreds of thousands of civilians have been killed in the war, mostly by the regime and its powerful allies. Millions more have been displaced both inside and outside of Syria.
The brutal tactics pursued mainly by the regime, which have included the use of chemical weapons, sieges, mass executions and torture against civilians have led to war crimes investigations.