Turkish President Recep Tayyip Erdogan has warned Russia and Iran that an attack by Syrian government forces and their allies on Idlib province, the last rebel stronghold in the war-ravaged Middle Eastern country, would result in a massacre.
Erdogan spoke at a summit with Iranian President Hassan Rohani and Russian President Vladimir Putin on September 7 in Tehran.
They were meeting to discuss the situation in Idlib amid concerns that an expected government offensive in the northwestern province would cause severe bloodshed, major civilian casualties, and a humanitarian catastrophe.
Rohani said that the fight in Syria should continue until all extremists are "uprooted," especially in Idlib, but that the battle there should not harm civilians.
Hours before the three presidents met, the Britain-based Syrian Observatory for Human Rights said that air strikes hit parts of Idlib province on September 7, the day the three leaders met to discuss the situation there.
Putin -- travelling with Foreign Minister Sergei Lavrov, Defense Minister Sergei Shoigu, and foreign policy aide Yury Ushakov -- met with Erdogan before the trilateral talks.
There are tens of thousands of rebels in Idlib province, which borders Turkey. An estimated 10,000 Al-Qaeda-linked fighters are among those rebels, and Idlib is also home to about 3 million civilians — nearly half of them displaced from other parts of Syria.
Russia and Iran are both allies of the Syrian government, which has set its sights on retaking Idlib in what it sees as the next critical step to clinching a military victory in the seven-year civil war that has killed more than 400,000 people and displaced millions.
For the Syrian government and Russia, the province is also strategically important because it borders Latakia province, Assad's main stronghold and the site of Russia's biggest air base in the country as well as its naval facility.
Turkey backs many of the rebel groups in the province but recently moved toward its negotiating partners in declaring that the Al-Qaeda affiliate Hayat Tahrir al-Sham, formerly known as the Al-Nusra Front, is a "terrorist organization" that should be eliminated.
The top Iranian diplomat for Syria policy told Iranian media that Idlib posed a dilemma because it had to be liberated from "terrorists" but the security of millions of civilians had to be protected.
Hossein Jaberi Ansari, a senior aide in the Foreign Ministry, said the presidents would seek a compromise and that "Turkey and Iran are sufficiently mature politically to facilitate such a compromise."
Russian officials have said "terrorist" groups should be "liquidated," but the Russian military has also said it is seeking to separate out extremist fighters from other rebel groups supported by Turkey.
As Putin and Erdogan were arriving in Tehran, the Syrian Observatory for Human Rights said air strikes were targeting positions belonging to rebel groups in the northern Hama and southern Idlib provinces.
It said strikes on September 7 destroyed a building near the town of al-Habeet used by the Islamist Ahrar al-Sham group, which is separate from Hayat Tahrir al-Sham, resulting in a number of casualties.
Assad's government has been massing thousands of troops in preparation for an assault. Russia, which has provided air support to the Syrian army since 2015, has made a big show of force by moving 10 warships and two submarines off the coast of Syria.
A spokesman for the National Front for Liberation, a Turkey-backed rebel alliance, said the group's fighters are prepared for battle but are looking to Turkey for efforts to prevent the attack and "protect Idlib."
The rebels expect a major humanitarian crisis, a large wave of displacement and heavy casualties if a Russia-backed offensive takes place, spokesman Najib al-Mustafa said.
Western powers, which never formally entered the conflict other than to back Kurdish-led militias instrumental in ousting the extremist group Islamic State (IS) from its northern stronghold in 2017, have largely watched the brewing battle in Idlib from the sidelines.
The United States, France, and Britain have warned, however, that they would take action if Assad uses chemical weapons in his assault on Idlib, as he allegedly has done in battles to retake other parts of the country.
Russia and Syria and have denied planning a chemical weapons attack, but U.S. special adviser for Syria Jim Jeffrey told reporters on September 6 that "there is lots of evidence" that chemical weapons are being prepared by government forces in Idlib. He said that "any offensive is to us objectionable as a reckless escalation" of the war.
Putin said in Tehran that "terrorists" were planning "provocations," in Syria, including the potential use of chemical weapons -- repeating a frequent Russian claim that has been dismissed by the United States and other Western governments. He did not provide evidence.
The UN has warned that an all-out offensive in Idlib will lead to death and destruction even greater than that seen previously in Syria, including the displacement of another 800,000 civilians -- most of whom are likely to seek refuge in nearby Turkey, which already hosts 3.5 million war refugees.
Erdogan has warned against such a catastrophic outcome, and has much at stake in efforts to prevent it at the Tehran summit.
Staffan de Mistura, the United Nation's Syria envoy, made a personal appeal to Erdogan and Russian President Vladimir Putin to work together to find a "soft solution to this crisis."
"We look to Russia, Turkey, Iran to come with hope to the civilians in Idlib," he said. "There are indeed many more babies than there are terrorists in Idlib. There are a million children."
De Mistura's call on the negotiators -- in particular the main power broker, Russia -- to protect civilians was echoed by eight European countries in a joint statement on September 6.
Iranian fighters have provided critical support for Assad throughout the war.
The presidents of Turkey, Russia, and Iran have met to discuss Syria three times in less than a year. Their previous meetings, in Sochi and Ankara, established so-called de-escalation zones in several areas, including Idlib, that temporarily reduced violence.
All these agreements were later violated, however, as Syrian troops backed by Russia and Iran moved to retake those areas after strafing them with artillery and air strikes -- a pattern which could be repeated in Idlib.
In regaining control over other parts of Syria in the last year, Russian-brokered surrender deals offered safe passage for tens of thousands of rebels and their families to Idlib, which is why the province became the last bastion of the armed resistance.