Syrian political and armed opposition figures are set to gather on Tuesday in the Saudi capital Riyadh in an effort to form a united front ahead of negotiations with the Syrian government scheduled to commence on January 1st.
This will be the first time representatives of various factions meet since unrest erupted in Syria in March 2011.
Saudi Arabia has invited 100 representatives to attend, including the Saudi-sponsored hardline fundamentalist Jaish al-Islam (Army of Islam), which is not defined as a terrorist group although it adheres to the same puritan Saudi ideology as Islamic State and al-Qaeda's Jabhat al-Nusra, both designated terrorist organisations.
The attendance is not certain of Ahrar al-Sham, an amalgamation of fundamentalist factions that emerged after the 2011 Egyptian uprising and before the troubles began in Syria. The group consists of scores of factions fighting in Idlib province, Hama and Aleppo, and it co-operates with groups adhering to the Free Syrian Army brand as well as Nusra.
Jaish al-Islam and Ahrar al-Sham are the largest armed factions which combined can field some 27,000 fighters.
US-backed Syrian Kurdish Protection Units, the military wing of the Democratic Union Party (PYD), which have seized control of a wide band of territory on the Syrian side of the Syria-Turkish border, have not been invited due to objections from Turkey, Riyadh's ally in the struggle against Syrian president Bashar al-Assad's government.
This omission could prompt the PYD to align itself with Damascus. The Kurds have co-operated with the Syrian government and regular army in some battles and share control of Hasakeh city in the northeast.
The objective of the gathering "is to agree on a common and clear position concerning the future of Syria, the transition and the stance [on the fate of] Bashar Assad", said Samir Nashar, a member of the Istanbul-based National Coalition.
This goal is at odds with an increasing number of western powers involved in the Syrian conflict, which give priority to forging a common front to wage war on Islamic State – also known as Isis – which has seized tracts of territory in Syria and Iraq.
Factions convening in Riyadh follow the Saudi line by demanding Mr Assad's departure before the beginning of the transition period, while the US, France and Germany, which focus on the anti-Isis battle, argue that Mr Assad, who governs 65 per cent of Syrians still in the country, will have to take part in the transition and perhaps stay on for some time.
The position of the western powers has drawn closer to that of the domestic Syrian opposition as well as those of Russia and Iran, which have bolstered the struggle of the Assad government against insurgents.
US secretary of state John Kerry and his French counterpart Laurent Fabius have urged Riyadh and Turkey to press insurgent factions to negotiate ceasefires with the government and join the fight against Islamic State.
Saudi Arabia and Turkey not only sponsor the opposition National Coalition but also provide weapons and funds for fundamentalist forces fighting the regime, even though some share recruits and arms with and battle alongside Nusra and Islamic State. This has prompted Iran to warn that the Riyadh conference could legitimise groups that should be included on the "terrorist list" due to be compiled by Jordan.
Last month a meeting of 17 powers in Vienna adopted a road map for resolving the Syrian crisis by imposing a ceasefire on all but Islamic State, Nusra and other "terrorist" factions and negotiating on a transitional authority that would take power within six months and hold elections after 18 months. The fate of Mr Assad was not settled at this gathering.
