The UN is bracing for a mass movement of 900,000 people who are expected to flee if the government launches a large-scale offensive in Syria's last rebel-held region of Idlib.
Idlib's most powerful armed faction is the Hayat Tahrir al-Sham (HTS) jihadist group, which Ankara officially designated a "terrorist" group last month.
Though Germany has said it will not simply comply with Russian requests for reconstruction help in Syria, the issue could provide leverage in stopping the Idlib offensive.
A full-scale air and ground offensive is likely to send waves of refugees surging toward the sealed Turkey border, coinciding with the onset of winter.
Idlib is part of an arc of territory at the Turkish border representing the last major area held by insurgents who have fought President Bashar al-Assad through more than seven years of war.
According to the report, Turkey was represented by Ibrahim Kalin, Mr Erdogan's special adviser; Germany by its national security adviser John Hacker; France by Philipe Etienne, senior diplomatic counselor for French President Emmanuel Macron; and Russian Federation by Yuri Ushakov, senior adviser to Mr Putin.
The presidents of Russia, Iran and Turkey met last week in Tehran to consider alternatives, but failed to reach a consensus.
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The Syrian Observatory for Human Rights said calm mostly prevailed again on Friday.
Syrian activists meanwhile said new military reinforcements had arrived to beef up Turkish observation points inside Idlib.
Government and Russian forces bombed towns and villages in the province earlier this week, killing more than a dozen civilians and damaging two hospitals. It is seeking to gain time to support its efforts, it said, to separate radical militants from moderate opposition groups it backs.
Although the Foreign Minister did not specify where the meeting would take place, several local media outlets reported it would be held in Sochi, the Russian city that hosted a Turkey-Iran-Russia summit in November previous year.
Weaponising chlorine is prohibited under the Chemical Weapons Convention, ratified by Syria, and under customary worldwide humanitarian law, the investigators said in their latest report.
He also stressed that it's the responsibility of Turkey now to separate the terrorist groups from the moderate ones.
"Between 1 and 12 September, the available information indicates that the strong increase of the hostilities and the fears of a new escalation have led to the displacement of most of 38,500 people", said the office of humanitarian Affairs of the UN (Ocha). Civilians and fighters have poured in, shuttled out of towns and cities where Assad's military crushed rebels with the help of Russian Federation and Iran.