Syrian rebel factions have demanded that President Bashar al-Assad have no part in any transitional government, issuing a joint statement on Thursday after two days of crucial talks in Riyadh.

"Participants have insisted that Bashar al-Assad and his aides quit power with the start of the transition period," said the statement, referring to a plan set out in Vienna last month to have a "credible, inclusive and nonsectarian" transitional government in place in the country by June 2016.

Participants, however, did say there that they are "ready to negotiate with representatives of the Syrian regime... within a specific timeframe that would be agreed on with the United Nations," the statement added.

The talks were the largest between rebel factions since the outbreak of war in 2011. But the result - a demand for Assad to quit as president of Syria - keeps them firmly at odds with the president's backers, Russia and Iran, exacerbating a key issue in ending the war and echoing previous rebel demands that contributed to the failure of talks in Geneva last year.

The statement came after a day of apparently fractious talks with one of the participants, Ahrar al-Sham, withdrawing saying it had a "religious and national obligation" to refuse to work with "regime sympathisers". It complained that those at the table included only a "small number of jihadi rebel factions" and "people who do not hide their support for the Syrian regime".

"As we withdraw from the conference, we are calling on other Mujahedeen and revolutionary groups to make a historic stance on the side of their religion, nation and people," Ahrar al-Sham said in a statement.

"[Other groups] must take into consideration the sacrifices that were made to achieve their goals."

Reports later said Ahrar al-Sham had returned to the fold and would attend future negotiations with Assad, although this was not confirmed.

PT: I’m now hearing [unconfirmed] reports that Ahrar al-Sham have reversed & agreed to sign the #Riyadh statement. Unclear if it’s amended. — Charles Lister (@Charles_Lister) December 10, 2015

'Stronger position'

Saudi Arabia’s Foreign Minister Adel al-Jubeir had earlier said the talks put Syria’s opposition in a “stronger position” ahead of peace talks scheduled to take place in New York later this month.

But al-Jubeir said President Assad had two choices - he must either leave power after negotiations or be forcibly removed.

Speaking in Riyadh, al-Jubeir said the Syrian people would not accept any other outcome after years of devastating war.

New negotiations on Syria’s future must take place before a 1 January deadline set last month during a landmark meeting of 20 states in Vienna.

US Secretary of State John Kerry had also hailed the talks as “very constructive,” saying he hopes they will help in the progress towards finding a political solution to the conflict ahead of the New York talks.

Points of principle

The Riyadh talks brought together 103 delegates from armed and non-armed groups – but excluded Kurdish groups.

On Thursday, the final day of the talks, delegates agreed on seven key “points of principle” as a starting-point for ongoing negotiations.

The first of these, agreed without a strong Kurdish presence at the table, is the “unity of Syria as a land and as a people”.

Delegates also agreed on the civilian and democratic nature of a future Syrian state, which would retain the current state’s apparatus but completely restructure the army and security force.

A source from the Free Syrian Army delegation also confirmed to Associated Press that the participants agreed to demand the withdrawal of all foreign fighters from the country. Lebanon's Hezbollah, Iranian militias, and Russian special forces are now known to be fighting for Assad. American and UK special forces have also been authorised to target the Islamic State group in Syria with the US-led coalition bombing IS since last year.

US-based intelligence services organisation The Sufan Group this week announced that up to 30,000 foreign fighters have joined jihadist organisations across the world, including some 8,000 in the Middle East.

The committee was to be made up of 23 people – six from the Syrian National Coalition, six from various rebel groups, six from local activists from across the country and five independent officials, according to a source quoted by Al Jazeera.

In the wake of Ahrar al-Sham’s withdrawal from the talks, it remains unclear whether the seven points of principle remain binding.