The presidents of Iran, Russia and Turkey held talks in Tehran on Friday, set to determine the future of Idlib province amid growing fears of a humanitarian disaster in Syria’s last major rebel bastion.

Shortly after arriving in Iran, Russian leader Vladimir Putin and his Turkish counterpart Recep Tayyip Erodgan sat down for a summit with Iranian President Hassan Rohani, an AFP photographer said.

They met in a conference centre in the north of the Iranian capital as a Syrian regime offensive against the last opposition stronghold appeared imminent.

The three countries are guarantors of the Astana process, a track of negotiations launched after Russia’s game-changing 2015 military intervention which has eclipsed the Western-backed Geneva negotiations led by the UN.