Russian Federation and Iran backed a military offensive to reclaim the last major rebel-held area of Syria, while Turkey called for a ceasefire to prevent mass casualties among the province's estimated 3.5 million population.
After seven years of war, Idlib has become the focus of a struggle that has spilled well beyond Syria's borders, transforming the conflict into one of the most complex and consequential battlefields of modern times.
The Turkish president said earlier this week he has plans to ditch the USA dollar in trade with Iran and instead use local currencies. It's an operation that many warn will cause major bloodshed among a vulnerable population of 3 million people.
Both groups reported that Russian aircraft targeted the area.
On Saturday, dozens of Russian air raids hit southern and southeastern areas of Idlib province, the Syrian Observatory for Human Rights monitoring group said.
The Trump administration's new envoy to Syria, Jim Jeffrey, told the Reuters news agency this week that he was "very sure that we have very, very good grounds to be making these warnings" about an upcoming assault on Idlib, and that while "any offensive is to us objectionable as a reckless escalation". However, many of those now besieged in Idlib say they are not willing, even under bombardment, to risk crossing into government-run areas.
The observatory said 19 barrel bombs had been dropped and there was also shelling from government areas.
A summit in Tehran on Friday between Russian President Vladimir Putin, Iranian President Hassan Rouhani and Turkish President Recep Tayyip Erdogan was seen as an opportunity for a diplomatic solution before a full assault on Idlib.
With US-led support, Syria's Kurds played a key role in the war against the Islamic State group, during which they seized large swathes of northern and northeastern Syria. "That would be absurd", she told the council. But above all, the summit highlighted the stark differences among these allies of convenience, with Putin and Rouhani opposing Erdogan's call for a cease-fire.
"President Bashar al-Assad of Syria must not recklessly attack Idlib Province".
Mr Putin said Damascus "has a right and must eventually take under control all of its national territory", while Mr Rouhani warned against a "scorched earth" policy but said "fighting terrorism in Idlib is an unavoidable". Russian Federation also wants to maintain its regional presence to fill the vacuum left by the United States and its long uncertainty over what it wants in the conflict. Estimates predict that up to 700,000 people in Idlib could be displaced during an offensive. It insists it is the rebels who are planning a chemical attack.
Another "tool" in the USA arsenal is economic pressure. "Here in Idlib, on one street you have people from all 14 governates in Syria", said Mostafa. But sanctions have been ineffectual since they first began to be applied during the Obama administration.
There was no immediate reaction from fighters in Idlib.
The dilemma facing the rebels and Sunni jihadist militants is that there are few places left to flee to should the Assad regime attack.
"There is no military solution to the Syrian conflict", Haley said in a statement on Wednesday.
In a statement describing the air-assault that took place Friday night in Syria, a spokesman for the US military's Central Command, responsible for all American forces in the Middle East said it was an effort to "demonstrate the capability to deploy rapidly, assault a target with integrated air and ground forces, and conduct a rapid exfiltration anywhere in the Operation Inherent Resolve combined joint operations area", said Navy Capt. Bill Urban, using the name for the coalition to defeat ISIS in a separate statement. He also charged militants in Idlib province with preparing their own chemical weapons attacks.
Eight aid agencies warned on Friday that in the coming offensive "it will be the most vulnerable who will pay the heaviest price, with women, children, and the elderly in Idlib unlikely to be able to move to safety".
"My fear is that past will be prologue with the Trump administration", says Frederic C. Hof, diplomat in residence at Bard College in NY and State Department special adviser on Syria during the Obama administration.
"Terrorists are trying to establish a foothold there with the help of foreign powers and stay there forever", Erdogan said Friday.