ANKARA: Turkish President Recep Tayyip Erdogan will host his Russian and Iranian counterparts for a summit on Syria in Ankara on September 16, the presidential spokesman said.

Despite being on opposing sides in the Syrian conflict, Syria regime backers Iran and Russia have worked closely with rebel supporter Turkey to find a political solution.

"The president will host a three-way summit with the participation of Russia and Iran in Ankara," spokesman Ibrahim Kalin said late Wednesday.

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 rebel stronghold of Idlib in Syria's northwest.

Kalin said there was "no question" of moving one of its 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.

That deal has come under increasing strain since the Syrian government began heavy bombardment of Idlib in April, raising fears in Turkey of a mass refugee exodus from the region of three million people.

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 Putin, Rouhani and Erdogan since November 2017.

Kalin said Erdogan would speak on the phone with Putin in the coming days, adding that preparations were being made for another call with US President Donald Trump. —AFP