By Tulay Karadeniz and Dominic Evans
ANKARA (Reuters) - The Russian-Turkish agreement to avert a Syrian government offensive against Idlib hinges on the response of jihadist fighters in the region and could unravel quickly if Moscow and Ankara cannot jointly impose their plan on the Islamist groups.
Turkey, desperate to avoid all-out conflict and a humanitarian crisis on its southern border, forged the surprise deal with Russia on Monday to set up a demilitarised zone around Idlib, staving off an imminent attack.
Ankara has for months called for a targeted campaign against the jihadists who control parts of Idlib, instead of a broad offensive against a region which is also home to 3 million civilians and tens of thousands of Turkey-backed rebels.
The deal announced in Sochi after talks between Russia's President Vladimir Putin, a strong backer of the Damascus government, and President Tayyip Erdogan gives Turkey the opportunity to put that proposal into effect.
However time is short - the two leaders want to set up the demilitarised zone by mid-October - and it is not clear how they will enforce their plan to disarm and remove hardline Islamist insurgents.
Announcing the deal, Putin said the zone will run along the frontline separating rebel-held Idlib and Syrian government forces. "Radical militants" will withdraw and heavy weapons will be removed from them and other opposition groups, he said.
The Russian president did not say how the radical groups would be persuaded to cooperate, or where they might be sent.
Turkey has a dozen military posts in the Idlib region and announced last October that it would isolate "terror groups" from "moderate rebels" there. Nearly a year on, it has little to show for its effort, and analysts say it is not clear how Monday's agreement will change prospects.
"I have to say this is a very, very small possibility," said Metin Gurcan, a security analyst and retired Turkish military officer, adding that the jihadist would be persuaded only through a show of strength rather than dialogue.
The most powerful rebel force in Idlib is Tahrir al-Sham, a coalition of Islamist groups made up of Syrian and foreign fighters and dominated by the former al Qaeda affiliate known as Nusra Front.
Putin named Nusra as one of the groups which would be targeted by the measures, but neither he nor Erdogan identified which other Islamist fighters could be affected. Turkey said on Tuesday it would discuss the matter with Russia, suggesting that no agreement has been reached.
One diplomat who follows Syria forecast that the Sochi deal would only stabilise Idlib for a few months. "It is just a postponement of the question that does not have a crystal clear solution," the diplomat said.
"NOWHERE TO GO"
For the foreign jihadists, Idlib is the last haven in Syria after President Bashar al-Assad, backed by his allies Russia and Iran, reversed years of rebel gains and drove his opponents from remaining pockets in southern and western parts of the country.
"The main problem is the foreign fighters, they have nowhere to go," said Sinan Ulgen, a former Turkish diplomat and analyst with Carnegie Europe.
Ulgen said Turkey appeared to be pinning its hopes on possible splits among the jihadists, with Syrian fighters more amenable to disarming than the foreigners.
"The main principle is divide and rule, attempting to separate, at the granular level, the different constituencies," Ulgen said. "They may all be jihadists, but they may have different inclinations in terms of this demilitarisation."
An insurgent source in Idlib said there were different views emerging within Tahrir al-Sham over whether to cooperate.
The group's stance is crucial because once its decision-making Shura Council rules on the issue, Tahrir al-Sham wields enough power to impose its will on other jihadist fighters in Idlib, including foreigners, the source said.
"If there is an agreement between Tahrir al-Sham and Turkey, the matter will proceed easily," the source said.
Ankara designated the group a terrorist organisation last month, but the source said there were indications that Turkey and Tahrir al-Sham could cooperate on the ground, noting the ease with which Turkish military convoys pass through Idlib.
The United Nations Syria envoy has said there are thought to be around 10,000 Nusra fighters in Idlib. There are other Islamist and groups fighting under the Free Syrian Army banner. With Turkish backing, they are now gathered under the "National Front for Liberation."
Gurcan said the Sochi agreement had granted Turkey a brief respite until the Oct. 15 planned implementation, but Russia would not hold back forever from tackling a region it calls a "nest of terrorists".
"Ankara has bought one month, and Russia has given it this time period. However Moscow is doing this for the last time," he said. "How is Ankara going to use that one-month period?"
(Additional reporting by Tom Perry in Beirut; Editing by Matthew Mpoke Bigg)