More than three dozen Syrian opposition groups have rejected a Russian-led initiative for talks next month in Sochi on ending Syria's war, AFP reported Tuesday (December 26th).

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 29th and 30th.

Syria's government swiftly said it would attend, but opposition groups have pushed back, calling it a Russian bid to eclipse a UN-led process in Geneva.

"We completely reject Russia's attempt to circumvent the Geneva track," the opposition groups said in a joint statement signed by 40 factions that was published Monday.

"We call on all forces to stand in one rank against these alarming dangers."

Mustefa Sejari, a top Mutasem Brigades figure, told AFP on Tuesday that opposition groups could not see Russia as an honest broker.

"From the beginning, we said whoever wants to play an intermediary and guarantor role in Syria needs to be neutral, fair and honest in its support of political transition," Sejari said.

"Russia has not done these things -- it is a partner in the killing of the Syrian people," he added.

The UN has yet to firmly endorse the summit.