The Syrian opposition said on Tuesday Russian President Vladimir Putin’s move to draw down his forces in the country could pave the way for an end to five years of fighting, although Moscow had not informed them of the decision.

Spokesman Salim al-Muslat told reporters that the Russian withdrawal could also help bring about an end to Syrian President Bashar al Assad’s “dictatorship and his crimes”.

Russia blindsided world powers on Monday by announcing that “the main part” of its forces in Syria would start to withdraw.

It was unclear what the withdrawal would mean for the outcome of the war or the future of Assad, who has regained ground from rebels with the help of heavy Russian air strikes.

U.S.-Russian cooperation had already prompted a lull in the war via a “cessation of hostilities agreement” that led to a sharp decline in fighting between rebels and the government in western Syria.

Muslat said a Russian pullout could have far-reaching consequences on the course of Syria’s war, saying that “what has kept Assad in power is the presence of Russian forces”.

Talks under way in Geneva are part of a diplomatic push launched with U.S.-Russian support to end a war that has killed more than 250,000 people, created the world’s worst refugee crisis, and prompted the rise of ISIS militants.

The Saudi-backed High Negotiations Committee’s main demand when it begins its first formal talks later on Tuesday with a U.N. special envoy will be the creation of an interim government without Assad under a U.N.-sponsored road map, Muslat said.

“Our concern is that negotiations begin today with a discussion of an interim government that would be a guarantee towards a pluralistic democratic state. When the regime talks about a national unity government this means Assad remains as a ruler in which ministers would be appointed by him.” The gulf is wide between the Assad government and rebel groups over a political transition with Damascus saying it will rule out any discussion of the president’s future at peace talks.