Peace talks gathering the Syrian regime and rebel groups began Monday in the Kazakh capital Astana, although rebels said they would not negotiate face-to-face with the government in the first session.
Representatives from the two sides sat at the same round table as Kazakh Foreign Minister Kairat Abdrakhmanov delivered an opening speech, an AFP correspondent saw.
Rebel spokesman Yehya al-Aridi told AFP earlier Monday that the opposition was backing out of the first direct talks because of the regime's continued bombardment and attacks on a flashpoint area near Damascus.
It remains unclear whether rebels could negotiate directly with the regime at a later session.
Rebels have said the talks would be focused on strengthening a frail nationwide ceasefire that was brokered last month by Russia and Turkey.
Damascus has meanwhile pushed for a "comprehensive" political solution to the conflict and insisted that rebels lay down their arms in exchange for an amnesty deal.
The Astana talks were organised by regime backers Iran and Russia and rebel ally Turkey.
Several rounds of failed negotiations in Geneva saw political opposition figures take the lead in negotiating with the regime.
But in Astana, the 14-member opposition delegation is composed solely of rebels leading the armed uprising, backed by nearly two dozen legal and political advisers.
More than 310,000 people have been killed and more than half of Syria's population displaced since the conflict erupted in 2011 after protests against the rule of President Bashar al-Assad.