The presidents of Iran, Russia and Turkey have started talks at a summit in Tehran to discuss the fate of Syria’s northern province of Idlib, the last rebel stronghold, which Damascus is determined to take by force.

Iran’s Hassan Rowhani, Turkey’s Recep Tayyip Erdogan and Russia’s Vladimir Putin are meeting to discuss Idlib, with Ankara determined to avoid a massacre there.

Ahead of the summit, Erdogan met his Iranian counterpart Rowhani, before they joined Putin for the trilateral talks.

Iran’s top diplomat responsible for Syria said he is hopeful that the three presidents will find a compromise.

Hossein Jaberi Ansari, a senior aide in the Foreign Ministry, told Iranian media that Idlib was a dilemma because on the one hand it had to be liberated from terrorists, but on the other the security of millions of civilians had to be protected.

The parties meeting in Tehran would bear both these aspects in mind to find a compromise, he said.

Turkey has supported the rebels in the Syrian conflict, while Iran and Russia support the regime of President Bashar al-Assad. “Turkey and Iran are sufficiently mature politically to facilitate such a compromise,” Jaberi Ansari said.

Syrian government troops and their allies have amassed troops near the Idlib countryside in preparation for a final assault.

The north-western province is strategically important for the government because it borders Latakia, a province that is the main stronghold of al-Assad and home to the biggest Russian airbase in the country.

Over the past three years, thousands of rebels and their families have been evacuated from different parts of Syria to Idlib under agreements with the government.

It is largely controlled by Hayat Tahrir al-Sham, an Islamist alliance led by an al-Qaeda-affiliated group.

It also has a population of 3 million civilians, a third of them internally displaced by the seven-year conflict.

The UN special envoy to Syria, Staffan de Mistura, warned last week that the presence of 10,000 al-Qaeda-linked fighters in Idlib does not justify an attack that could endanger civilians’ lives.

“A ruthless process is going on in Idlib. … God forbid, if these places are shelled by missiles, there will be a very serious massacre,” Erdogan said this week.

Friday’s summit would help resolve issues, he said, stressing the importance of cooperating with Russia while also warning of a potential refugee influx.

Turkey, which has 12 observation posts in Idlib, already hosts 3.5 million Syrian refugees.

Washington and Moscow have evaded responsibility of Idlib, Erdogan said. “The US passes the buck to Russia, Russia passes the buck to the US.”

US President Donald Trump warned the Syrian government against committing a “slaughter” in Idlib.

The Tehran talks should focus on “further joint efforts to ensure long-term stabilization” in Syria, including the “creation of conditions for the repatriation of refugees and internally displaced persons,” the Kremlin said.

Previous meetings by the leaders of Turkey, Russia and Iran have led to the establishment of so-called de-escalation zones in Syria, including Idlib. But the ceasefires were repeatedly broken.

In recent months, al-Assad’s forces, supported by Russian air power, have made territorial gains across the war-torn country against Western-backed rebels and militants, including Islamic State.