The presidents of Russia, Turkey and Iran will meet on Wednesday for a summit aimed at bringing peace in Syria.
Here is what you need to know about the trio's summit at the Black Sea resort of Sochi, hosted by Vladimir Putin ahead of parallel UN-led talks in Geneva set to be relaunched on November 28.
- Building on Astana talks -
Syrian regime backers Russia and Iran and rebel supporter Turkey have co-sponsored peace talks in Astana, the capital of Russian ally Kazakhstan.
With seven rounds of negotiations this year, the Moscow-initiated talks brought together representatives of the Syrian government and the opposition, including some key armed groups who had previously steered clear of other negotiations.
Unlike the Geneva talks which were politically focused and led to deadlock, the Astana diplomatic push concentrated on military issues.
While unable to halt fighting altogether, the talks did lead to a lowering of violence on the ground with the creation of four "de-escalation" zones.
Following its military intervention that allowed Damascus regime forces to get the upper hand on the ground, Moscow now wants to use the Astana result to relaunch a political process.
"There are three countries setting the future trajectory of Syria, and none are the US or an Arab country," said Randa Slim, an expert at the US-based Middle East Institute.
- Summit agreement? -
Ahead of the summit the trio in no way forms a united bloc: ongoing major differences between the powerbrokers will make the negotiating process difficult.
"Russia wants to have allies" at the Geneva negotiations, said Russian expert Alexei Malashenko. "This is proving to be difficult as the three (countries) need to come to an agreement: each has its own vision and its own interests."
"There is a chance to at least demonstrate that there are some common points," he said, but the parties will not be able to reach a "concrete agreement."
According to Russian foreign minister Sergei Lavrov, who has said he wants to relaunch the political process, the heads of states will have to discuss the Kremlin-sponsored "Congress of National Syrian Dialogue", which seeks to gather both the regime and the opposition in Russia.
The idea was first put forward during the last round of the Astana talks in October but was flatly rejected by the Syrian opposition, which has refused to hold any political discussions at the UN Geneva talks since 2014.
- What about Assad? -
All Syrian peace processes so far have come to a deadlock on the political issue at the centre of the conflict which has left over 300,000 dead in six years.
For Moscow and Tehran, Syrian President Bashar al-Assad's departure would lead to chaos, whilst for Turkey-backed rebels and the West, all solutions that include Assad after what they perceive as the regime's war crimes continue to be unfavourable.
But the Syrian leader, in power since 2000, is currently in a strong position on the ground. The United States and France no longer make his departure as much of a priority as they once did.
Even Ankara, despite calling for Assad to step down, could be more compromising behind closed doors in Russia.
"For now, it's more important for Turkey to keep its say in the future political negotiations than to have Assad depart from power," Timur Akhmetov, an Ankara-based Turkey expert at the Russian International Affairs Council, told AFP.
The Middle East Institute's Randa Slim said that "it seems like we are heading towards holding parliamentary elections... but that Assad's fate will be decided in elections after his current term ends." In other words, in 2021.
- Other collision points -
If Turkish President Recep Tayyip Erdogan is willing to be flexible on Assad's fate, it's because the Syrian president's future is not Ankara's sole priority.
For over a year now, Turkey appears to have been more anxious to stop the expansion of Kurdish Popular Protection Units (YPG) forces in northern Syria.
Ankara views the YPG as a Syrian extension of the outlawed Kurdish Workers' Party (PKK), whose fighters have carried out guerilla attacks on Turkish security forces for three decades. The PKK is blacklisted as a terror group by Turkey and its Western allies.
For the heads of state gathered in Sochi, "one of the principal differences is what form the Kurdish participation in Geneva will take," said Noah Bonsey, an analyst at the International Crisis Group.
"This question is currently being discussed and I do not see the Turks making progress on this point," Bonsey said.
He added that "it's hard to believe" the Sochi summit will make significant progress given the major differences between the three countries and the absence of other major players like the US, Saudi Arabia or Jordan.