The leaders of Turkey, Russia and Iran will meet next month to try to resolve differences over Syria that have prevented them from imposing a peace deal.
The meeting of the countries' presidents in Ankara on September 11 “would discuss all aspects of the Syrian crisis”, Alexander Lavrentyev, Russia’s special envoy for Syria, told Tass news agency.
The meeting will mark the second time this year that Turkey's Recep Tayyip Erdogan, Russia's Vladimir Putin and Hassan Rouhani of Iran have met to discuss their intervention in Syria.
The three have mostly sidelined the US on Syria since agreeing to co-operate on Syria in 2017.
But since then, the nations have struggled to agree on how to draw their spheres of influence.
The three are guarantors of the Astana process, which were talks mostly among themselves and supervised by Moscow to defeat "terrorism" and resolve the civil war.
The process, named after its venue in the Kazakhstan capital, contributed to freezing US-backed international peace talks in Geneva.
It focused on defeating the trio's idea of terrorists and produced mostly nominal ceasefires.
That allowed forces loyal to Syrian President Bashar Al Assad, with backing from Iran and Russia, to recapture territory from the moderate Free Syrian Army and militant rebel factions.
Since then, Russia and Iran have uneasily shared territorial influence, with Moscow allowing Israeli raids against Iranian targets in Syria.
Turkey has established a territorial sphere in the north, having pushed back the Kurdish militia it considers terrorists but who still control large parts of eastern Syria.
Since the three leaders met in the Russian resort city of Sochi in February, a war between Russian and Turkish allies intensified in the northern governorate of Idlib, the last rebel stronghold.
It was mostly taken over in the past three years by the Al Qaeda-linked Hayat Tahrir Al Sham.
An offensive backed by Russia and Iran on Idlib threatens to capture a major rebel town in the south of the governorate, although there are Turkish observation posts in the area.
The offensive has killed hundreds of civilians and driven masses to seek refuge near the Turkish border, rising tension between Moscow and Ankara.
Turkey has also angered Russia and Iran by negotiating with the US over a planned safe zone in areas of eastern Syria on its border.
The zone would remove territory from Kurdish militia and place Turkey close to, if not in control of, Syria’s major oil and gas resources.
Last December, US President Donald Trump announced a troop withdrawal from Syria but has since held off, leaving a reduced number of special forces in the east.
A senior Syrian opposition member close to Turkey said the picture “is confused perhaps more than any time before”.
He said differences between the three countries extended to the shape of the political order they wanted to impose in a settlement.
Russia and Turkey have largely filled a proposed, UN-supervised constitutional committee with their nominees, to the disadvantage of Iran, opposition sources say.
The committee will draw up a new Syrian constitution.
The opposition member said Turkey wanted the political process to result in the end of the Alawite-dominated Assad regime.
But Iran and Russia want the regime to continue, with Tehran adamant about Mr Al Assad staying on as leader, he said.
"Russia might not be sure Assad's continuity would result in any stability for the foreseeable future," he told The National from Istanbul.
Russia, Iran and Turkey will first have to solve a complicated situation where their troops and those of the US are not far from each other in Syria.
Turkey might not be in a hurry for the US to leave, despite public statements to the contrary.
Ankara might prefer negotiations with Washington over eastern Syria to again taking part in a scramble with Iran and Russia.
