BEIRUT: The United Nations envoy for Syria urged Syrian opposition groups at the opening of a meeting hosted in the Saudi capital Wednesday to come up with a united delegation for the Geneva talks later this month.

Staffan de Mistura spoke at the opening of the three-day meeting for the Syrian opposition in Riyadh, where they are expected to come up with a unified delegation and vision ahead of the Geneva talks on Nov. 28.

But the meeting has already been marred with disagreements. The notoriously fragmented opposition is divided by visions of a future role for the incumbent Syrian President Bashar Assad, the length of a transitional period as well as the constitution that will see the country move toward elections.

The conflict in Syria, now in its sixth-year, has all but been frozen amid a series of cease-fires. But a political solution has long been elusive.

Saudi Foreign Minister Adel al-Jubeir said in opening remarks that the opposition meeting comes amid an international consensus to reach a resolution.

"There is no resolution to the crisis without Syrian consensus that achieves the demands of the Syrian people and ends their suffering," al-Jubeir said, adding that a resolution must be based on U.N. resolutions.

The meeting is intended to come up with a unified vision ahead of the new round of peace talks in Geneva on Nov. 28. Russia, which has welcomed the Saudi efforts to unify the opposition, is also hosting a meeting expected to bring the opposition and Syrian government together in early December.

On Wednesday, Russia president is meeting with Iranian and Turkish counterparts to discuss the Syria conflict, amid a diplomatic push from Moscow to reach new resolutions. Russian President Vladimir Putin hosted Syrian President in Sochi a day earlier, in which he discussed with him potential new initiatives. Iran and Russia are main backers of Assad; while Turkey has supported the opposition.

Disparate opposition delegations are attending the meeting in Riyadh. Some of them are backed by Gulf countries, who had sided with the anti-Assad rebellion, while others have been backed by Russia. Another opposition group is backed by Egypt, which has kept contacts with the Syrian government.

The Saudi-owned Al-Arabiya Al-Hadath TV said some members of the Russia-backed delegation withdrew from the meeting. A member of the delegation Qadri Jamil said they withdrew to object other delegations putting conditions on the talks, including limiting a future role for Assad. The Russia-backed opposition is promoting political reform under Assad's rule.