More than three dozen Syrian rebel groups, including influential Islamists, have rejected a Russian-led initiative for talks next month in Sochi on ending Syria's war.
Russia and Iran, both key allies of Syria's regime, agreed with opposition backer Turkey on Friday to hold a "Congress of National Dialogue" in the Black Sea resort of Sochi on January 29 and 30.
Syria's government swiftly said it would attend but rebels have pushed back, calling it a Russian bid to eclipse a United Nations-led process in Geneva.
"We completely reject Russia's attempt to circumvent the Geneva track," the rebels said in a joint statement published Monday.
"We call on all forces to stand in one rank against these alarming dangers."
It was signed by 40 factions, including Islamist powerhouse Ahrar al-Sham and groups that have been backed by the United States such as the Mutasem Brigades.
Some of the factions played a significant role in the rebellion since the war broke out in 2011 but most have either been sidelined by other groups or control only small pockets of land.