The country's state-run IRNA news agency described the summit as potentially offering an "agreement on peace and security" in Syria.
The area in northwest Syria is home to some 3 million people - the majority of whom were displaced from other regions - as well as an array of Sunni rebels dominated by Islamist militants linked to al-Qaeda.
Idlib's population has swelled as the regime chalked up a series of victories in other parts of the country, reaching evacuation deals that saw tens of thousands of people bussed to the northwestern province.
De Mistura said there were about 10,000 fighters with UN-recognized terrorist organizations now in Idlib.
Erdogan continued by saying that a rational solution in Idlib that will address everyone's concerns needs to found. Those included a workshop used by the militants for construction of drones, a warehouse of explosives as well as a storehouse, where they kept their MANPADs.
For Russia and Iran, both allies of the Syrian government, retaking Idlib is crucial to completing what they see as a military victory in the civil war after Syrian troops recaptured almost all other major towns and cities, largely defeating the rebellion against Assad.
The warning comes as the United Nations urged Russian Federation - a key supporter of Assad that has complained about militants in Idlib targeting its own facilities - and Turkey to help avert a "bloodbath" in the rebel-held province.
Iran, Russia and Turkey all have their own competing interests over Syria.
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She spoke previous year with senior adviser and presidential son-in-law Jared Kushner , who also hosted Wednesday's session. Kim wants the President to get behind prison reform legislation that will rejigger sentences so they fit the crime.
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The streets of Tehran were quiet on Friday, the second day of the Iranian weekend.
Russian President Vladimir Putin however, said that he was against a ceasefire because Nusra Front and Islamic State of Iraq and the Levant (ISIL) fighters located there were not part of peace talks.
For Turkey, the stakes couldn't be higher. The country hosts 3.5 million Syrian refugees and has closed its borders to newcomers.
"The battle for Idlib is going to be the final major battle", said Hilal Khashan, a political science professor at the American University of Beirut, told Reuters before the summit.
The UK-based Syrian Observatory for Human Rights said warplanes, which it believed were Russian, struck the southern countryside of Idlib and a village in nearby Hama province. The three leaders whose nations are all under USA sanctions have an interest in working together, but Idlib is complicated and they have little common ground.
"Any offensive is to us objectionable as a reckless escalation", he said, adding that "there is lots of evidence that chemical weapons are being prepared". The attacks prompted terrified residents to flee before a fully-fledged assault gets under way, said the monitor. Russia, which has provided air support to the Syrian Army since 2015, has made a big show of force by moving 10 warships and two submarines off the coast of Syria. While Idlib is expected to top the agenda, the trio are also expected to discuss mechanisms for minimizing the impact of USA financial pressure.
"The Trump Administration and the global community have made it clear that there is no military solution to the Syrian conflict", Haley told the Council, which was to hold another meeting Friday on the crisis in Idlib.