Turkish President Recep Tayyip Erdogan will host his Russian and Iranian counterparts for a summit on Syria in Ankara on September 16th, presidential spokesman Ibrahim Kalin said late Wednesday (August 21st).

The announcement of the meeting between President Vladimir Putin, Iranian President Hassan Rouhani and Erdogan comes at a time when Syrian forces have made advances into the last opposition stronghold of Idlib in Syria's north-west, AFP reported.

Kalin said there was "no question" of moving one of Turkey's 12 observation posts in Idlib, despite it being cut off from the rest of the province by the advance of Syrian forces this week.

"The ninth observation post remains in its place. All the other observation posts foreseen or put in place under the Idlib agreement will continue to operate where they are," Kalin said.

He was referring to a buffer zone agreement signed between Russia and Turkey last year that was supposed to protect Idlib from a government offensive.

The three presidents will discuss Idlib at next month's meeting, as well as the establishment of a constitution commission and how the political process should continue, Kalin said.

Their last meeting was in February and the September event will be the fifth summit between the three leaders since November 2017.