Around 140 opposition figures are gathered in Riyadh in a bid to form a unified delegation to meet representatives of Syrian President Bashar al-Assad's regime in Geneva on November 28.
Several rounds of talks hosted by the United Nations have failed to bring an end to the six-year war in Syria, which has killed more than 330,000 people since 2011 and forced millions from their homes.
The Riyadh talks also come as Syrian regime ally Russia is seeking to organise a "congress" to bring together Assad's forces and various opposition groups to reinvigorate the peace process.
In Riyadh, a Cairo-based Syrian opposition group agreed on Thursday to join ranks with other opposition groups and send a unified delegation to Geneva.
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The Cairo-based made the deal with other opposition clusters including the Saudi-backed High Negotiations Committee (HNC) -- the largest block in the opposition -- and the Istanbul-based National Coalition.
"The Cairo group has joined the main opposition delegation to Geneva," Ahmed Ramadan, head of the National Coalition's media department, told AFP.
"We are looking to form one delegation with fair representation. This is the point that is currently under discussion," said Qadri Jamil, head of the Moscow group and a former Syrian deputy prime minister.
A news conference scheduled this afternoon was postponed as meetings stretched into the evening in a bid to find consensus, according to one opposition member.
The delegates at the Riyadh meeting have been under heavy pressure to row back on some of their more radical demands after a series of battlefield victories that have given Assad's regime the upper hand.