Being invited to join the latest round of Syria talks in Vienna must feel like vindication for Iranian leaders.
It is the first time the United States has formally engaged with Iran on the Syrian crisis and it is a sign that Iran's political isolation is thawing.
But Iranian influence in Syria has come at a price.
An increasing number of high-ranking Revolutionary Guard officers have been killed in Syria, many of them on some of Syria's most active front lines.
They include one of Iran's best known generals, Hossein Hamedani, who was killed on the outskirts of Aleppo earlier this month.
It has led some Iranians to question their country's involvement in Syria and prompted the deputy commander of Iran's Revolutionary Guard to appear on television, trying to ease public concerns.
So, have major powers accepted Iran has a role to play in ending Syria's war? And how big a price has Tehran had to pay for its new found influence?
Presenter: Jane Dutton
Arron Reza Merat - Iran analyst for the Economic Intelligence Unit.
Hassan Ahmadian - Professor of Middle East Studies at the University of Tehran.
Julien Barnes-Dacey - Senior Policy Fellow in the Middle East and North Africa Programme at the European Council on Foreign Relations
Source: Al Jazeera