Saudi Arabia's effort to unite Syrian rebels in Riyadh next week will be a big test of its regional ambitions after years of bickering between opposition groups and serious misgivings about the initiative among major powers with a stake in the war.
Since King Salman took power in January, Riyadh has tried to position itself as leader of the Middle East's Sunni Muslims, most of whom want to see Syrian President Bashar al-Assad toppled and the influence of his Shi'ite ally, Iran, curbed.
Riyadh now sees an opportunity to shape the war in Syria after the Russian intervention, the European refugee crisis and the Paris attacks reawakened international engagement with the conflict and the threat posed by Islamic State.
"This conference is meant to change the situation on the ground," said a senior Western diplomat in the Gulf, pointing to the need to strengthen what he called the "moderate opposition" in Syria, which opposes both Assad and Islamic State.
Next week's gathering will be attended by around 65 members of the political and armed opposition, including around 15 representatives from armed groups. Of the two most powerful armed groups, Islamic State has not been invited and the al Qaeda offshoot Nusra Front is also not expected.
However, with Iran decrying the meeting as harmful to peace prospects, Turkey alarmed by the likely presence of Kurds, and Western countries concerned by the role that Islamists will play, Saudi Arabia may struggle to achieve that.