RIYADH, Saudi Arabia, Dec. 8 (UPI) -- Syria's major rebel groups are joining in Saudi Arabia in an effort to agree on a platform for peace negotiations next month.
The BBC reported preparatory talks began Tuesday in Riyadh as representatives from the main rebel groups, including Jaysh al-Islam and Ahrar al-Sham, arrived in the Saudi capital.
Saudi Arabia, a key financier to several Syrian opposition groups, is attempting to help form the various cells into a coherent, unified delegation for upcoming talks with the Syrian regime of President Bashar al-Assad.
Many world powers involved in recent talks in Vienna -- including Assad's allies, Russia and Iran -- want to see peace negotiations begin by at least Jan. 1.
Following a meeting Tuesday with U.N. Secretary-General Ban Ki-moon in Paris, U.S. Secretary of State John Kerry expressed hope the talks would begin as early as next week.
The goal is for the main opposition and the government to reach a political solution so they can combine efforts against their common enemy, the Islamic State.
U.S.-backed Syrian Kurds were not invited to the conference but are simultaneously holding independent talks concerning Syria's future.
The Nusra Front -- al-Qaida's Syrian affiliate and a member of Jaish al-Fatah, an alliance of rebel groups that includes Ahrar al-Sham -- was not invited either.
Some Western-backed rebel groups, however, will attend. The Turkey-based Syrian National Coalition -- which calls for Assad's departure and the establishment of a transitional governing body in Syria -- is one. Another is the Southern Front alliance, which the BBC quoted as saying it was the "moderate voice and the strong arm of the Syrian people."
Conservative Islamist factions such as Ahrar al-Sham and Jaysh al-Islam want the Assad government out and an Islamic state in its place, but the leader of Jaysh al-Islam later softened his stance, saying the Syrian people should decide their future.
"We want to prove to the international community that keeps criticizing our efforts to unite, that we can agree and move forward with one goal," Khaled Khoja, head of the SNC, told Al Jazeera. "That is the aim of the Riyadh talks. We want to prove we can unite."
The Riyadh conference -- which comes amid ongoing attempts by pro-Assad forces, bolstered by Russian air power, to regain territories across Syria that were lost throughout the year -- was reportedly condemned by Iran, Saudi Arabia's regional rival, who said it would harm upcoming peace talks.