After months of delays, a "Geneva II" conference meant to broker an end to the Syrian civil war has been scheduled to begin on January 22 in Geneva, Switzerland, the United Nations said Monday morning.

But which parties will attend - a subject that helped push back the conference for months - wasn't immediately clear.

The conference would bring representatives from Syria's government and elements of the opposition to negotiate an end to the fighting that has wracked Syria since March 2011.

Yet the opposition is hardly a single group; it consists of numerous factions that often oppose each other. The al Qaeda-linked groups Islamic State in Iraq and Jabhat al-Nusra have made substantial gains in Syria in recent months, especially in the north, tilting the balance away from more moderate factions of the rebel Free Syrian Army.