Syria's political and armed opposition are urging their decade-long backer Turkey to reaffirm its support for their cause, after the highest-level talks in public between Ankara and the Damascus government since the Syrian war began in 2011.
Turkey has provided steadfast support and a home base for political opponents of the regime of President Bashar al-Assad while training and fighting alongside armed rebels against Syrian government troops.
But the Turkish and Syrian defense ministers met in Moscow on December 28, with migration and Kurdish militants based on Syria's border with Turkey on the agenda, according to a Turkish official.
Unease among Syria's opposition
That has prompted unease within Syria's armed and political opposition.
The head of Hayat Tahrir al-Sham, a hardline insurgent group, said in a recorded video address published on Monday that talks between Syria, Russia and Turkey were a "dangerous deviation."
Ahrar al-Sham, another Islamist faction, said that while it "understood the situation of our Turkish ally," it "cannot even think of reconciling" with the Syrian government.
He had assured it of Turkey's continued support "to Syrian opposition institutions and Syrians in the opposition-held areas," said Abdurrahman Mustafa, the head of the Turkey-backed opposition's "interim government."
A senior Turkish official told Reuters that it had seen the "reactions" of rebel factions to the meeting but that "Turkey determines its own policy."
"It is unrealistic to expect an immediate result from the first meeting of ministers," the official said.
Turkish-Syrian rapprochement seemed unthinkable earlier in the conflict, which has killed hundreds of thousands of people, drawn in numerous foreign powers and splintered Syria into various zones of influence.
Turkish President Tayyip Erdogan has called Assad a terrorist and said there could be no peace in Syria with him in office, while Assad has called Erdogan a thief for "stealing" Syrian land.
But meetings between the two countries' security chiefs last year paved the way for the defense minister summit.