Russia and Turkey agreed on Monday to a create a "demilitarised zone" between Syrian rebels and government forces in the northern city of Idlib, staving off a potential humanitarian catastrophe in the last rebel stronghold.
During a summit in the Black Sea resort of Sochi, Russian President Vladimir Putin and his Turkish counterpart Recep Tayyip Erdogan came to an agreement that "radically-minded" opposition fighters, including formerly al-Qaeda-linked ones that control parts of Idlib, would be withdrawn.
Russian and Turkish military police would then carry out coordinated patrols of the zone – which would be 12 miles deep – from October 15, Mr Putin said.
Both sides have already established observation points near flashpoints in the province but the latest development marks increased cooperation between the two countries, which back opposing sides in the war.
Moscow is keen on strengthening ties with Turkey, at a time when Ankara’s relations are at their lowest with the US.
"I believe our joint statement following this meeting will give the region a new hope," Mr Erdogan said after the meeting.
"At the moment, I believe, not only our region but also the world is looking at Sochi today," he added.
Turkey, which supports and funds opposition groups in Syria, had been told by Russia to separate the estimated 10,000 Islamist Hayat Tahrir al-Sham (HTS) fighters from the 30,000-40,000 more moderate ones in Idlib.
But Turkey called instead for measures to target hardline militants while protecting civilians and avoiding an indiscriminate assault. "Let’s not create an excuse and take a step like bombing there," Mr Erdogan said.
Syria’s ambassador to the United Nations in Geneva, speaking earlier on Monday, said the Bashar al-Assad government remained determined to drive HTS from the province.
"Our government wants to give priority to reconciliation and to give all necessary measures in order to ensure safe corridors, and to secure the lives of civilians and to provide the basic needs of civilians in cooperation with UN humanitarian agencies," Hussam Edin Aala said.
The deal would see any offensive postponed until at least December 15, however it was unclear whether the Syrian government or its Russian allies were still planning an all-out assault.
Russia-backed forces of the regime have massed around Idlib in recent weeks, which had sparked fears of an imminent air and ground attack to retake the last major opposition bastion.
Dozens were killed and injured in a flurry of Russian and Syrian air strikes earlier this month, however there has been little offensive action since then.
As many as three million civilians are trapped in Idlib, buffered on three sides by Syrian government forces and a closed Turkish border to the north.
The United Nations had warned that an all-out offensive would result in the "worst humanitarian crisis this century".
There has been growing pressure on Russia to rein in Assad’s forces. Turkey warned a fresh exodus of civilians fleeing fighting could see a fresh wave of refugees, which Mr Erdogan last week threatened to send to Europe.