Amid fears of what could potentially be a humanitarian catastrophe if Syrian President Bashar Assad's forces conduct a full scale attack on the last rebel stronghold in Idlib, a region home to around 3 million people, the presidents of Russia, Turkey and Iran are meeting on Friday in Tehran to discuss potential diplomatic solutions.

On Thursday, Iran's speaker of parliament said he hoped that leaders of the three countries would be able to reach a "final agreement" on the events happening in Idlib. However, as the war between Assad's forces and Syrian rebels comes to an end, each country has its own vision for a role in Syria's future.

Turkey has warned against an attack on Idlib, both out of humanitarian and strategic interests. For one, an attack on the region would send a wave of refugees across the Turkish border, located less then 60 kilometers from Idlib. Ankara also wants to maintain long-term influence in northern Syria, for example in the Kurdish province Afrin, where Turkey has established a military presence.

Iran, as an ally of Assad, wants to cement its influence in Syria in the potential aftermath of government forces wiping out the rebellion. Iran's Minister of Defense Amir Hatami and Minister of Foreign Affairs Mohammad Sarif both visited Damascus recently, reportedly closing a military cooperation pact and reiterating Iran's commitment to staying in Syria and helping rebuild the war-torn country.

Read more: Russia relaunches Idlib bombing campaign

However, Iran's goal of maintaining influence in Syria may be unrealistic. According to Iranian journalist and Middle East observer Habib Hosseinifard, Israel, the US and Saudi Arabia will take every measure to ensure Iran leaves Syria, or at least reduces its influence.

"If Idlib is captured and Iran's presence is no longer relevant, Russia and Syria will both begin rethinking Iran's role," he told DW.

For Turkey, if they can maintain a long-term military presence and a level of control over Kurdish border regions, Hosseinifard believes Ankara would be happy to see Iranian influence in Syria decline.

Russia relies on Iran – for now

Iran and Russia together have ensured the survival of Assad. At the same time, however, Russia is trying to improve its relationship with Israel, a country that insists Iran leave Syria. It remains to be seen which position Moscow will take toward a permanent Iranian presence in Syria.

Margarete Klein, an expert on Russia and security policy at the German Institute for International and Security Affairs (SWP), told DW that Russia does not have an interest in Iran having a stronger position in Syria. "Russia and Iran are increasingly becoming competitors for shaping the political, economic and military order in Syria," she said.

Read more: Syria's Idlib: UN warns of chemical weapons, jihadis and humanitarian catastrophe

"At the same time, Russia has little interest in completely removing Iran as a military actor in Syria," added Klein. "Russian forces composed primarily of the air force and special forces, are dependent on Iranian-supported ground troops in Syria."

Russia also doesn't have the resources to force Iranian and pro-Iran forces out of Syria or weaken their overall presence in the region.

"Moscow's position in the Middle East is based on maintaining good relations with all actors in the region," said Klein, adding that Russia is trying to find a good middle ground by getting Iran to stay out of Syria's southern border region with Israel. "Meanwhile, it tolerates Israeli military strikes against Iranian positions in Syria."

Iran's weakened position in Syria

Iranian journalist Hosseinifard is of the opinion that the foreseeable end of the war doesn't leave a lot of room for Iran to exercise military power and that the time of Iran's Revolutionary Guards in Syria is coming to an end.

For Syria, it will be difficult to begin rebuilding if they must first contend with the US and Israel over Iran.

Read more: Iran and Israel's Syrian shadow war laid bare

"For the US and Israel, the withdrawal of Iran from Syria is a primary condition for financial assistance, along with the restoration of the country's sovereignty," said Hosseinifard, adding that Syria needs hundreds of billions of dollars in aid.

"This is outside of Iranian and Syrian power," he said. "For the West to be ready to support Syria and enable the return of refugees, Syria will first have to change its Iran policy."