UNITED NATIONS - U.N. Secretary-General Antonio Guterres appealed Tuesday for the parties in Syria to avoid a full-scale battle for Idlib.
Idlib is the last so-called "de-escalation zone in Syria," Guterres told reporters. "It must not be transformed into a bloodbath."
Some 3 million civilians are living in the northwestern governorate, and the U.N. has repeatedly warned that there will be a humanitarian catastrophe if there is a military escalation there.
Russia, Iran and Turkey are known as the Astana guarantors - they oversaw the creation one year ago of four de-escalation zones in Syria that were supposed to be safer for civilians. They included parts of Idlib, Hama, eastern Ghouta and southern Syria. Only Idlib remains, the others have been militarily brought back under regime control.
Iran's President Hassan Rouhani, center, flanked by Russia's President Vladimir Putin, left, and Turkey's President Recep Tayyip Erdogan, pose for photographs in Tehran, Iran, ahead of their summit to discuss Syria, Sept. 7, 2018.
Guterres appealed directly to the troika.
"It is important that those - especially the three guarantors of the Astana process - find a way in which it is possible to isolate terrorist groups. And it is possible to create a situation in which civilians will not be the price paid to solve the problem of Idlib."
He said he understood that the situation in the governorate is unsustainable - the U.N. estimates some 15,000 terrorists are mixed in among Idlib's residents - but that "fighting terrorism does not absolve warring parties of their core obligations under international law."
Earlier, the U.N. Security Council met at Russia's request so it could be briefed on the outcome of last Friday's summit of the presidents of the Astana group. It was the third meeting on Idlib in the past week.
Turkey's U.N. ambassador renewed his president's calls to preserve the Idlib de-escalation zone and called for an immediate cease-fire.
"There is no doubt that an all-out military operation would result in a major humanitarian catastrophe," Ambassador Feridun Hadi Sinirlioǧlu told the council. "Such an operation would trigger a massive wave of refugees and tremendous security risks for Turkey, the rest of Europe and beyond."
Turkey already hosts 3.5 million Syrians, and its hospitality has been stretched to its limit.
He urged the international community to support Turkey's call for a cease-fire.
U.S. Ambassador to the United Nations Nikki Haley speaks to members of the media at U.N. headquarters in New York, Sept. 10, 2018.
U.N. Ambassador Nikki Haley said the United States would consider any large-scale military assault on Idlib as a "reckless escalation" and called on Russia to prevent it.
"Russia has the power to stop the catastrophe looming in Idlib," Haley, a member of President Donald Trump's cabinet, told council members. "They have the power to stop the killing."
She said the Astana process had failed to stop the violence or promote a political solution.
"Russia, Iran and (Bashar al-) Assad are demolishing Idlib and asking us to call it peace," Haley said. "But here's the reality: Astana has failed."
She warned of potential military escalation and said that if the Assad regime, backed by Russia and Iran, continue on this path, "the consequences will be dire."
A boy tries on an improvised gas mask in Idlib, Syria, Sept. 3, 2018.
Haley also repeated her warning that Washington would not tolerate the use of chemical weapons.
For weeks, the Russians have been accusing the West of conspiring to carry out a chemical weapons attack through rebel groups and the civil society first responders, the White Helmets, and then blaming the Assad government for it as a pretext for military intervention.
Moscow's U.N. envoy fired back, accusing some council members of escalating rhetoric.
"The wordings started sounding basically along the lines that saying force against a sovereign state - Syria - can be used, and not only related to alleged use of chemical weapons, but basically also if there is a military operation in Idlib," Vassily Nebenzia said. "We are not talking about a military operation. It's an anti-terrorist operation."
Russia's U.N. Ambassador Vassily Nebenzia speaks to reporters after attending a Security Council meeting, Aug. 9, 2017, at United Nations headquarters.
The Russian ambassador noted that de-escalation zones were created as "temporary entities," not permanent ones.
"Sooner or later, they were to be replaced, first by local truces. And in those cases where that did not take place, by an anti-terrorist operation, which happened in other de-escalation areas, which are currently under the control of Syrian authorities."
Nebenzia dismissed plans by the Syrian regime to use chemical weapons, saying they no longer had any, and if they did use them, it would be an "invitation" to Britain, France and the United States to strike the country. He also claimed to have "irrefutable proof" that the Syrian opposition was planning a chemical attack, but he did not offer it.