Turkey failed to convince Iran and Russia to agree to a ceasefire in Idlib yesterday, paving the way for a likely assault by the Assad regime on the Syrian province in coming days.
The United States also said it had "lots of evidence" that regime forces were preparing chemical weapons for possible use in Idlib.
Speaking at a major summit in Tehran, Recep Tayyip Erdogan, Turkey's president, warned his Russian and Iranian counterparts that an attack on the densely populated province would lead to a "bloodbath" and a surge of refugees into Turkey.
However, the summit's final communique made no mention of a ceasefire and when Erdogan made a last-minute effort to insert the term into the text he was publicly rebuffed by Russia's president Vladimir Putin.
Putin said he could not commit to one because there was no guarantee that terrorist groups in Idlib "will stop shooting or using drones".
Meanwhile, Russian or Syrian airstrikes on south-west Idlib yesterday killed a jihadist fighter and a shepherd, according to the Syrian Observatory for Human Rights.