The powerful Islamist insurgent group Ahrar al-Sham said on Wednesday that a Syrian opposition meeting in Saudi Arabia must insist that President Bashar al-Assad face justice and that Syria's "institutions of oppression" are dismantled.
The group, whose founders had links to al Qaeda, is taking part in the meeting in Riyadh with other members of Syria's fractured opposition and rebel groups, aimed at forging a common stance over planned talks expected early next year to end four years of civil war.
Its uncompromising statement, issued as delegates gathered in the Saudi capital, reflected the divisions which the two-day meeting will have to overcome if it is to agree a joint approach.
The meeting was due to start on Wednesday at a heavily secured hotel in Riyadh. Journalists had to leave the site on Tuesday as delegates arrived.
Ahrar said some of those invited were "closer to representing the regime than the people and the revolution", and the rebel representation at the Riyadh talks did not fairly reflect their presence on the ground.
Opposition figures say Saudi Arabia initially invited about 65 participants, 15 of them from rebel and insurgent groups.
They include powerful Islamist factions such as Islam Army and Ahrar, which still fights alongside the al Qaeda's Syrian wing, Nusra Front, while espousing a nationalist agenda.
A dozen groups which fight under the loose umbrella of the Free Syrian Army will also attend as will political opposition figures in exile, who have limited influence inside Syria, and some from Syrian-based opposition groups.
Ahrar said it would stand by demands including "the complete cleansing of the Russian-Iranian occupation of Syrian land, and the sectarian militias which support it".
It called for the "overthrow of the Assad regime with all its pillars and symbols, and handing them over for fair trial".
Syrian security and military institutions must also be dissolved Ahrar said, putting it at odds with world powers which agreed in Vienna last month that state institutions be kept intact in any transition of power.
The Vienna meeting, attended by Russia, the United States and powers from Europe and the Middle East, also agreed on committing to Syria's "non-sectarian character".
The fighting pits mainly Sunni Muslim groups against Syria's army, supported by Shi'ite fighters from Iran and Lebanese group Hezbollah. Assad is from Syria's Alawite minority, and the country also has Christian and Druze populations.
Ahrar said Syria's "Islamic identity" should be maintained.