AMMAN/ANKARA: Wary of a confrontation with Turkey that could suck Moscow into a military quagmire, Russia is likely to take a gradual approach to helping the Syrian government capture the last rebel bastion of Idlib, analysts and diplomats say.
President Bashar al-Assad's army, aided by heavy Russian air strikes, has swept through dozens of towns in Idlib province in the last two weeks in the deepest advance in years, forcing tens of thousands to flee to the Turkish border.
But Russia is unlikely to lend its military muscle for a full-on advance on densely populated Idlib city.
Such a push would help Assad regain full control of Syria, which he and his late father before him ruled for a total of nearly 50 years, but it would also risk a major confrontation with Turkey, which backs opposition forces in the war.
Instead, Russia appears intent on "biting" chunks of rebel turf in a piece by piece approach, a senior Western intelligence source told Reuters,
Turkey, which already hosts 3.6 million Syrian refugees, has threatened military action if Assad's forces do not retreat by the end of the month and has reinforced Turkish outposts in the region and set up new ones to try to slow the advance.
"The regime has come very close to Idlib (city)," a Turkish official told Reuters. "The rules of engagement in Syria changed, a new era has started now."
The crackle of gunfire can now be heard by the more than a million inhabitants living in the city, many of them Syrians displaced by government assaults on their territory.
"People everywhere are terrified, people are sleeping in the streets and cars, there is no place to stay," Ibrahim Samaan al Hajj, a grocer in the city said.
Officials from Turkey and Russia are due to discuss the offensive on Saturday as tensions rise after eight Turkish soldiers were killed in Syrian shelling on one outpost, prompting Turkish troops to respond.
A costly battle for the provincial capital does not appear to be Moscow's priority.
"Russia is concerned with opening major highways that are symbols of sovereignty for the regime," said Syrian military defector general Ahmad Rahhal. "Falling in the Idlib (city) quagmire is very costly militarily and a humanitarian catastrophe with one million people inside the city."
Moscow will be the one to decide if and when to move on Idlib city at some stage, a step that risks unleashing a bloodbath and deepening the humanitarian crisis, opposition military commanders and Western intelligence sources said.
Syrian ground troops aided by Iranian-backed militias coming from Aleppo are now on the fringes of Idlib city after taking Maarat al-Numan and Saraqeb near the strategic M4-M5 road Aleppo to Hama and Latakia on the Mediterranean coast.
"For the time being it's important that they control the highway, and I think it's an accommodation they can reach with Turkey," said Ozgur Unluhisarcikli of the German Marshall Fund.
He said the takeover on Idlib city is a "matter of time but we are not there yet" because the Syrian army is overstretched.
The battle for Idlib is a crucial stage of a war that has killed hundreds of thousands of combatants and civilians, made millions refugees in their own country or overseas, and fractured the wider Middle East since it broke out in 2011.
The fate of the region has been the focus of Russia-Turkey deals involving Iran since 2017 aimed at sparing its three million inhabitants all out war.
Turkish officials said the new advance imperils understandings under a 2018 pact that left Turkey, which has expanded its influence in Syria, to secure control of rebel-controlled highways and handle the thorny fate of jihadists. Moscow accuses Ankara of failing to live up to its obligations.
At a recent meeting with some 40 Turkey-backed rebel commanders held in Reyhanli along the border, Turkish intelligence told rebels that talks with Moscow had failed and to prepare for the worst, a source who attended the gathering told Reuters, adding that Idlib city was "a red line".
The city has been mostly spared the aerial bombing of the latest two-month old campaign that has triggered the exodus of nearly 600,000 people from areas further south and east.
Western military experts said Moscow has used a "scorched earth" aerial bombing maneouvre that has hit hospitals, schools and other infrastructure in mostly rural areas of the province. But such tactics could prove more difficult to use in the city.
"If there is going to be a battle in Idlib, there will be a bloodbath, the jihadists will fight with all their strength and we will see more suicide operations," Abu Baraa al-Shami, a nom de guerre of a senior commander with Hayat Tahir al Sham, told Reuters in a text message via Internet messaging.