Government forces have been concentrating on Idlib for days and seemed ready to launch what could be the last major battle of the civil war that has shattered Syria since 2011.
After retaking a succession of rebel strongholds across the country this year, the government of President Bashar al-Assad has set his sights on Idlib.
The most powerful armed faction in the province is the jihadist group Hayat Tahrir al-Sham and neighboring Turkey is trying to use its influence to prevent a major offensive against it.
"The negotiations between Turkey and HTS are still ongoing," said the head of the Syrian Human Rights Observatory, Rami Abdel Rahman, based in Britain.
Russia, whose military intervention in 2015 in support of Assad helped the government recover much of the lost ground in the first days of the seven-year conflict, wants the jihadist team to dissolve, he said.
"This is the condition established by Moscow to avoid a broad offensive … Its launch depends on the failure or success of these conversations with HTS."
In commentaries published in his Ibaa propaganda agency, HTS seemed to leave the door open to a negotiated agreement.
"The issue of dissolution, if it ever takes place, is one that would be discussed internally by the alliance's advisory council, but not dictated by local or foreign parties," he said.
"We at HTS are struggling to find an effective solution in the liberated Syrian north that protects our people from a possible offensive by the criminal regime and its allies."
While Turkey actively sponsors rebel forces in Idlib, its influence over the former al-Qaeda affiliate is less clear and Abdel Rahman warned that the chances of success were slim.
"Turkey's relationship with HTS is complicated, but it can be better framed as cooperative animosity," said analyst Elizabeth Teoman of the Institute for the Study of War.
Turkey, Russia and its Iranian regime counterpart operate "observation points" in Idlib as part of a "de-escalation" agreement agreed last year aimed at reducing bloodshed in the province.
But with a looming regime offensive, the Turkish military has reinforced its 12 monitoring posts.
During a press conference with his Saudi counterpart in Moscow on Wednesday, Russian Foreign Minister Sergei Lavrov insinuated that the assault could be imminent.
"It is necessary to de-link the so-called moderate opposition from the terrorists and, at the same time, prepare an operation against them while minimizing the risks to the civilian population," Lavrov said.
"This abscess must be liquidated."
& # 39; Humanitarian catastrophe & # 39;
Iran's top diplomat also held previously unannounced talks with Turkish President Recep Tayyip Erdogan on Wednesday.
The Minister of Foreign Affairs, Mohammad Javad Zarif, met with the Turkish strongman for an hour, but little was leaked about the nature of the discussions.
The Syrian Foreign Minister, Walid Muallem, was in Moscow on Thursday to discuss and reiterated the "determination of his government to liberate all Syrian territory."
Russian media reported this week that Moscow has been reinforcing its military armada in the region and currently has 10 warships and two submarines in Syrian waters.
The prospect of a massive offensive supported by Russia in a province that is home to some three million people, half of them already displaced from other parts of Syria, has raised fears of a new humanitarian tragedy.
The UN chief, Antonio Guterres, said on Wednesday he was "deeply concerned about the increasing risks of a humanitarian catastrophe in the case of a large-scale military operation in Idlib."
One of the fears is that the regime will resort to the use of chemical weapons, as it did during an offensive against the rebels in the eastern Ghouta enclave earlier this year.
The UN peace envoy in Syria called a humanitarian corridor on Thursday.
"Once again I am prepared … personally and physically to get involved … to ensure that this temporary corridor is feasible," Staffan de Mistura told reporters in Geneva.
Another is the presence in the province of a large number of combatants and civilians who have preferred to leave their homes instead of submitting to the Damascus regime.
Idlib has been used as a relief valve for evacuees from other rebel pockets, such as East Ghouta, after its negotiated surrender to the regime.
But combatants who reject similar offers of surrender to Idlib will have nowhere to go, which increases the chances of even more deadly battles if a full offensive is launched.
"The rebels, as well as desperate civilians, have taken refuge in Idlib, but now there is no other 'Idlib' in which they can flee," said the Soufan group of experts.