The talks will see an opposition delegation composed exclusively of rebel groups negotiating with the regime of Bashar al-Assad.
Hosted in the Kazakh capital Astana, the talks will see an opposition delegation composed exclusively of rebel groups negotiating with the regime of Bashar al-Assad in an initiative sponsored by rebel backer Turkey and regime allies Russia and Iran.
Though the talks have been welcomed by all parties in the conflict, delegates from both sides are heading to Kazakhstan with apparently opposing ideas about the goals, with Assad insisting Thursday that rebels lay down their arms in exchange for an amnesty deal.
Although Assad said the talks would prioritise reaching a ceasefire, Damascus has insisted it will seek a "comprehensive" political solution to the conflict that has killed more than 300,000 and displaced over half of the country's population.
The rebels meanwhile say they will focus solely on reinforcing a frail nationwide truce brokered by Moscow and Ankara last month.
Moscow said this week that the objective was to "consolidate" the ceasefire and to involve rebel field commanders in the "political process" to end the bloodshed, creating a basis for a new round of UN-hosted negotiations in Geneva next month.
Syria's UN ambassador Bashar al-Jaafari, an experienced negotiator involved in past failed talks in Geneva, will head the regime delegation in Astana.
The United Nations' peace envoy for Syria, Staffan de Mistura, will also attend, alongside representatives of Russia, Turkey and Iran.
Mohammad Alloush of the Jaish al-Islam (Army of Islam) rebel group -- whose rebel commander cousin Zahran Alloush was killed in an air strike claimed by the regime in December 2015 -- will lead a "military delegation" of around eight people.
They will be backed by nine legal and political advisors from the opposition High Negotiations Committee (HNC) umbrella group.
But key rebel group Ahrar al-Sham said it would snub the Astana talks over ceasefire violations and ongoing Russian air strikes on the country.
Ahrar al-Sham nonetheless said it would support decisions taken by other rebel groups represented at the talks if they were "in the interest of the nation".
The talks, which could last days, come a month after the Syrian regime, bolstered by its allies, took full control of second city Aleppo from rebels in its biggest victory in more than four years of fighting.
With stakes high and outcomes unclear, the Syrian opposition is wary that the regime could use the rebel groups' inexperience in political talks to its advantage in Astana, a European diplomatic source told AFP.
"There is genuine worry in the opposition that the representatives of rebel groups, which are not at all used to these types of international negotiations, will be dragged into a political solution that will play into the hand of the regime," the source said.
A negotiator in previous ceasefire agreements, Washington was last month sidelined from sponsoring the nationwide truce brokered by Russia and Turkey after months of disengagement from the conflict.
US President Donald Trump's team has been invited to Astana but has not yet officially responded.
Washington's absence has seen Moscow and Ankara join efforts on the Syrian crisis despite lingering disagreements over Assad's future and other aspects of the conflict.
After overcoming a rift in relations following Turkey's downing of a Russian warplane in Syria in November 2015, the two countries this week conducted their first joint strikes against Islamic State group targets in an operation Moscow hailed as "highly effective".
Kremlin spokesman Dmitry Peskov said in an interview aired Saturday on Russian state television that deals that could help end the conflict in Syria were "unlikely" to be struck in Astana because "too many parties are involved in the process."
Iran, the talks' third sponsor, will be represented by Deputy Foreign Minister Hossein Jaber Ansari, the country's Isna news agency reported.
Analysts say Iran, a longtime ally of Assad, views the Astana talks as an opportunity to increase its influence in the region after playing a crucial role in the symbolic recapture of Aleppo.
France and Britain will be represented at the ambassador level, the European diplomatic source said.
A representative of EU foreign affairs chief Federica Mogherini said Friday that "we will be there" without giving details about the delegation.
Divergent agendas and the absence of some key players and high-level officials cast uncertainty on how the Astana talks could serve as a building block for next month's Geneva negotiations.
"The success or failure of Astana is not predetermined," Russian Middle East expert Boris Dolgov told AFP.
"If something can be achieved in Astana, I think that a portion of the armed opposition will participate in the Geneva talks."