The leaders of Russia, Turkey and Iran, the co-sponsors of the Astana peace process for Syria, met in Tehran on Friday for their third summit. The leaders had one specific item on their agenda: The fight to liberate Idlib from extremists from Jabhat Al-Nusra and bring this province, the last bastion of the opposition, under the control of President Bashar Assad. The question of Idlib severely tested the unity of the conclave. President Recep Tayyip Erdogan of Turkey was reluctant to back an all-out attack on the area that hosts 3 million people, including about 100,000 extremists. He feared a bloodbath and refugees, along with extremists, fleeing to his country in their thousands; an onerous burden given that Turkey already has 3 million Syrian refugees. Differences among the leaders became apparent at the concluding press conference, when Erdogan abruptly intervened to insist that the joint statement refer to a “cease-fire” so that extremists would get the chance to surrender. Russia’s Vladimir Putin responded by saying it was doubtful they would “stop shooting or stop using their drones,” in reference to the drone attacks on Russian bases at Tartus and Hmeimim. However, to accommodate Erdogan, the joint statement was amended to call on all armed groups to surrender their weapons. The outcome of the Tehran summit is just one more move on the complex Syrian chessboard, on which several players with diverse and competing interests are pushing for maximum advantage as the scenario approaches its endgame. Russia is fully committed to the Assad regime and seeks to retain its military presence and political influence in Syria. Iran is also a solid partner of the Assad government and wishes to maintain its presence on Syrian territory, which keeps it on the frontline against Israel while ensuring its influence in Lebanon and Palestine. Both Russia and Iran are opposed to the US presence in Syria. The Tehran summit ensures the attempt to take Idlib will commence shortly, but a strong US intervention in Syria could plunge the Middle East into a serious conflagration. Talmiz Ahmad Turkey, a NATO member, has found itself increasingly at odds with the US, which continues to consolidate its presence in territory controlled by Syrian Kurdish forces at the Turkish border. The US has also expressed concern over the proposed Turkish purchase of the S-400 missile system from Russia, and has slapped sanctions on Ankara due to the detention of an American pastor, who Turkey accuses of working with the outlawed Kurdistan Workers’ Party (PKK). Given this contentious background, in the run-up to the Tehran summit Russia worked hard to bring together these diverse players. Besides high-level meetings of Russian officials in Ankara, Moscow hosted the foreign ministers of Saudi Arabia and Syria and engaged with the leader of the moderate Syrian opposition. Russia also highlighted the importance of addressing the refugee crisis in meetings with officials of Jordan, Lebanon and Turkey, all of which are hosting several million people who have fled Syria. Earlier, in the fighting in southern Syria, Russia had accommodated Israel’s interests by ensuring that Iranian and Iran-backed forces were kept about 100 kilometers from the border of the occupied Golan Heights. Russian diplomats also interacted extensively with their American counterparts in Washington, Moscow and Geneva to ensure they are on the same page on Syria. Here, the picture is hazy. The general mood in Washington is not to allow Russia to score any military or political successes in Syria. Thus, the US has refused to back any attack on Idlib, emphasizing the humanitarian calamity this would create, despite Al-Qaeda-affiliated extremists being located there in large numbers. Trump warned in a tweet last week against the Syrian regime “recklessly” attacking Idlib, and later said that the US would be “very angry” if civilians were slaughtered. Russia has been particularly concerned that the US would use the excuse of a chemical attack to launch a military assault on Syrian and perhaps Iranian forces in Syria. Hence, Russian officials, including Putin, have been warning for some weeks that extremists could use toxic chemicals to instigate such an American attack. The Russians have gone even further: They have bolstered their forces in the Mediterranean with 25 warships and two submarines and have carried out large-scale exercises off the Syrian coast. Russia has also publicly criticized the consolidation of the US presence in Syria east of the Euphrates, in territory under Kurdish control, seeing in this an attempt to partition Syria. The US has responded by enhancing its own military presence in the Mediterranean and the Gulf. The attempt to take Idlib will commence shortly. It will not be an all-out assault but will follow the earlier Syrian pattern of moving forward village by village, so that casualties can be minimized and opposition elements can surrender. Jabhat Al-Nusra leaders have pledged to fight to the last man, so some large-scale fighting may become inevitable toward the end, particularly when Syrian forces surround Idlib city itself. The US response to these developments remains uncertain. While Trump remains viscerally hostile to Iranian influence in Syria, his officials are opposed to any Russian achievement in the country. A strong US military intervention in Syria could plunge the Middle East into a serious conflagration. Talmiz Ahmad is an author and former Indian diplomat who holds the Ram Sathe Chair for International Studies, Symbiosis International University, Pune, India. 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