Talks in the Kazakhstan city of Astana have begun with the Syrian Opposition insisting that discussions will only centre around the ceasefire that it says is being violated chiefly by Iranian-backed militias in Syria.
The Syrian rebel delegation say they have no plans for direct face to face talks with representatives of the Damascus government in Astana, a rebel source said on Monday.
The Syrian opposition delegation, representing as many as 12 factions, have expressed a desire to adopt a more conciliatory stance but claim to be held back by the continuing hostility of the Iranian and the Syrian governments.
The talks are also sponsored by Russia, Turkey and Iran, but the US, the EU, Saudi Arabia and the UN have been sidelined. UN Syria envoy Staffan de Mistura will however be present and the and the US is being represented by its ambassador to Kazakhstan.
Russia faces a new set of challenges as it attempts to move from participant in the conflict to peace broker. Mohammed Alloush, the leader of the opposition delegation, said the failure of Moscow to put pressure on Iran and the Syrian government to end what the opposition says are widespread violations of the Turkish-Russian brokered ceasefire would be a blow to its influence in Syria.
Russia claim that the talks process stand a better chance to succeed than previous efforts led by the UN, partly because the military balance has changed and partly because the talks with political leaders representing the opposition but often living outside Syria.
With the talks formally due to end at lunchtime on Tuesday - early in the morning UK time - any agreement is unlikely to spread beyond the terms for deepening the ceasefire and providing humanitarian access, as well as agreeing on broad principles for a future Syria.
But the talks may reveal the extent to which tensions between Tehran and Moscow over the future of Syria can be contained. So far, there has been silence, for example, over whether the Iranian-backed Hezbollah should be forced to quit Syria.
Russia and Iran are both seeking to exploit the military and political victory with commercial and military deals with Assad.
The opposition has been disappointed by what it calls Moscow's inability to fulfil its role as deal guarantor and put pressure on militias led by Lebanon's Hezbollah group, saying this threatens to wreck the ceasefire deal brokered in December.
Sources: Guardian UK, Reuters, BBC