For the first time since the nuclear deal, Iran and US negotiators will sit the same table. Experts say Tehran's presence is crucial, but they doubt the two sides will find common ground on the Syrian civil war.
It took more than four years, 250,000 lives and millions of refugees, but for the first time, all of the major players will sit down at the same table and discuss a road map to end the civil war in Syria.
For the talks that begin Friday in Vienna, The United States has agreed to accept Iran's place at the negotiating table - and Iran has agreed to negotiate. Egypt, France, Germany, Iraq, Lebanon, Russia, Saudi Arabia, Turkey and the UK have also said they will participate in the talks.
"It is a clear sign that the nuclear deal is opening up areas for the world powers and Iran to cooperate managing the regional crisis," Seyed Hossein Mousavian, who served as Iran's ambassador to Germany and as spokesman for its nuclear negotiations with the European Union, told DW.
Washington had rejected Iran's inclusion in Syria negotiations twice before. But as the conflict drags on with no end in sight, the United States has been forced to acknowledge there's no viable solution without Iran, according to Saied Golkar, an Iran expert at the Chicago Council on Global Affairs.
"Right now, everybody realizes that the situation is not getting better," Golkar told DW. "It's getting worse day by day, and they realize that Iran is the only country on the ground helping Assad to survive. You cannot ignore Iran."
Syria détente unlikely
For Tehran, the costs for its military intervention are adding up. Three Revolutionary Guard commanders, including two generals, have been killed this month in Syria.
"Day by day they bring back the dead bodies of commanders," Golkar said. "They realize it's very expensive to do that. The popularity of this military intervention is decreasing in Iran. This has led the government to come to the negotiating table with the US."
There has been a détente in US-Iranian relations that culminated over the summer in the nuclear accord, which provides Tehran with sanctions relief in exchange for scaling back its nuclear activities. According Majid Rafizadeh, the will to compromise demonstrated in the nuclear talks won't likely extend to the Syrian conflict.
"In Syria, the geopolitical and strategic objectives and gaps are too deep to bridge between the two sides," Rafizadeh, an expert on Iran and Syria at Harvard University, told DW. "In addition, there exist so many players beside Iran and the US: regional and global state actors, as well as more than 1,200 non-state actors are involved in the war."
Iran and Russia have long viewed President Bashar al-Assad's regime as the only authority in Syria that can create stability, going so far as to support him with direct military intervention.
In contrast, the United States, as well as its European and Sunni allies have long viewed Assad as the source of violence and instability, rather than its solution. Washington, however, has begun to soften its position. In March, Secretary of State John Kerry acknowledged that the US will likely have to negotiate with the Assad regime as part of a power transition in Syria.
According to Golkar, there are pragmatists in Iran, led by President Hassan Rouhani, who advocate a political solution to the Syrian civil war and are even willing to consider a future without Assad in power. But they are locked in a battle with hardliners in the Revolutionary Guards, who continue to back Assad and believe in a military solution.
Ayatollah Khamenei is balancing the interests of the two camps, Golkar said, but Foreign Minister Javad Zarif's planned attendance at the Vienna talks must have been blessed by Khamenei. This indicates that the supreme leader is at least willing to contemplate a diplomatic solution.
"They are ready to abandon Assad, if the solution involves the Alawites, the Shias, and satisfies Iranian interests in the region," Golkar said. "If all of these countries reach a deal that will keep the Alawites in power, there is an opportunity that [Iran] will talk about Syria without Assad, but not without the Assad regime," he said.