Riyadh:Representatives from Syria's fragmented opposition began an unprecedented meeting hosted by Saudi Arabia on Wednesday seeking a united front for potential talks with President Bashar al-Assad's regime.

While not all groups were invited the two-day closed-door gathering marks the first time a broad range of Syrian political and armed opposition factions have come together since the conflict began in 2011.

The goal of the meeting attended by about 100 delegates is to form a unified bloc for talks with Assad that world powers hope can be held before January 1.

Saudi Foreign Minister Adel al-Jubeir who has repeatedly warned that unless Assad steps down peacefully he could be ousted militarily welcomed the delegates and expressed hope for a successful conclusion.

He then left and the Syrians began meeting among themselves at a heavily secured luxury hotel in Riyadh. The talks are chaired by Abdulaziz Sager a Saudi who heads the independent Gulf Research Centre in Geneva.

"The meeting saw a broad participation of Syrian opposition groups inside and outside Syria" the Saudi Press Agency reported.

The first day will focus on political questions including the general contours of a potential settlement while Thursday would be dedicated to discussing "terrorism a ceasefire and reconstruction" according to one delegate involved in organising the meeting.

There has been a growing diplomatic push for a resolution to the Syrian conflict which has killed more than 250000 people and forced millions from their homes.

Last month top diplomats from 17 countries -- including key backers and opponents of Assad -- agreed in Vienna on a fixed calendar that would see a transition government set up in six months and elections within 18 months.

Armed entities described as "terrorist" organisations such as Al-Qaeda's Syrian affiliate Al-Nusra Front and the Islamic State group were not invited to the Riyadh meeting.

But Ahrar al-Sham allied with Al-Nusra and whose invitation had prompted other groups to withdraw from the talks confirmed its attendance in a statement on Wednesday.

Ahrar al-Sham said that it had accepted the Saudi invitation despite the "lack of representation of jihadist factions at a level matching their... role" on the ground in the war-torn country.

The group warned that it "will not accept the results of this conference" unless they include "cleansing Syrian territories of the Russian-Iranian occupation and sectarian militia supporting them."

Kurds excluded

Iran and Russia are key backers of Assad's regime. Moscow has been conducting air strikes in Syria for more than two months while Tehran has supplied military assistance including "advisers" on the ground.

Shiite militia from neighbouring Iraq and Lebanon are also fighting alongside Assad's troops.

Ahrar al-Sham seen as one of the most powerful armed groups in Syria insisted the priority should be overthrowing Assad's regime dismantling military and security services preserving the country's unity and rejecting sectarianism.

The powerful Saudi-backed Jaish al-Islam (Army of Islam) rebel force which includes hardline Islamists said it was sending two delegates.

About 20 members of the Istanbul-based National Coalition the main opposition grouping are also taking part.

Riyadh insists invitations were extended to "all factions of the moderate Syrian opposition" including from all parties sects and ethnic groups.

But Kurdish organisations including the recently formed and US-backed Syrian Democratic Forces which includes Kurds Arab Sunni Muslims and Christians fighting IS were not invited.

Kurdish groups including the leading Democratic Union Party and other opposition movements have organised their own two-day conference that started on Tuesday in Syria's northeastern province of Hasakeh.

AFP