The potential massacre of civilians while trying to retake the last major stronghold of anti-government militants in Syria — namely Idlib Province — is a red line for Iran, says the Iranian chief negotiator in the peace process for Syria.

Hossein Jaberi Ansari, senior assistant to the Iranian foreign minister on special political affairs, told Press TV’s website in an exclusive interview published on Sunday that Idlib has a special status and has to be dealt with accordingly.

He said armed and terrorist groups have blended into a large civilian population there, which makes a retake of the region complicated and, in Iran’s viewpoint, eliminates the possibility of a quick fix.

Jaberi Ansari called the situation in Idlib “the epitome of the complexities of the Syrian conflict.”

“On the one hand, three million people are currently settled in Idlib. About half of that population is native to the region, and the other half comprises displaced persons from other areas,” he explained.

Of the second half, some are people normally displaced by the war, and others are the families of armed Syrian government opponents who have, along with their men, migrated there as part of previous deals, the senior Iranian official further said.

“On the other hand,” he said, “Idlib is the concentration point of numerous armed and terrorist groups” and as such, could not be left to itself.

Conflict erupted in Syria back in 2011, when a small group of opposition forces took up arms against Damascus. Soon, however, a mixture of international terrorists and paid mercenaries mingled with and then largely sidestepped the armed Syrian opposition groups, effectively turning the Arab country into a battlefield for foreign governments opposed to Syrian President Bashar al-Assad.

But the Syrian military, with advisory help from Iran and Russia — and a Russian aerial bombardment campaign — has retaken control of much of the country, and the conflict is generally believed to be winding down.

Over the past couple of years, armed groups that have been defeated in battles with the Syrian military have been bused into Idlib under agreements with Damascus. While those groups have mostly had to leave their heavy weaponry behind under those deals, they have been allowed to take their small arms with them.

Jaberi Ansari said that figures about the number of the armed and terrorist groups present in Idlib vary from one source to another, but he added they generally numbered in the tens of thousands.

He also said that the groups have widely different orientations, making it even more difficult to deal with the matter straightforwardly.

While the return of Idlib to Syrian government control could hypothetically take place swiftly with a full military assault, such an offensive would only lead to massive collateral damage, the Iranian official noted.

That, he said unequivocally, is a red line for Iran.

Any such massacre would also have “grave humanitarian and moral, as well as political costs, which is unacceptable,” he stressed.

Given the complexity of the matters in Idlib, he said, Iran sought in negotiations with its partners in the Astana process to make the case for a solution that is exclusive to Idlib and its special status.

Jaber Ansari believed the solution is phased and composite to include security, military, and political components that would have to be agreed upon.

He said that the Iranian proposal faced “initial resistance” from Russia and Turkey, Iran’s two partners in the Astana process that support the Syrian government and opposition, respectively.

He said Russia was inclined to resolve the Idlib matter more quickly, while Turkey sought to indefinitely delay any resolution of the issue.

Just as concerns were spiking about an all-out war and a potential humanitarian crisis in Idlib, and to everyone’s relief, Russia and Turkey reached a deal to avert disaster. At the end of a summit in Sochi on September 17, Moscow and Ankara agreed on, among other things, establishing a demilitarized zone in Idlib that would cover an expanse of 15-20 kilometers of land. Militants would have to entirely clear that area by October 15.

The agreement was welcomed not only by the Syrian government and opposition but also by international observers. Iran called it proof that “diplomacy works.”