Russia is working together with Saudi Arabia to unify the Syrian opposition, Russia's RIA news agency quoted Russian Foreign Minister Sergey Lavrov as saying on Friday.
Lavrov was speaking at a meeting with United Nations special envoy on Syria, Staffan de Mistura, who is visiting Moscow.
De Mistura said a new Syrian constitution will be one of the main items on the agenda for UN-sponsored talks in Geneva next week between opposing sides in the Syria conflict, RIA reported.
On Friday, Syrian opposition figures meeting in Saudi Arabia decided to send a united delegation to U.N.-brokered peace talks in Geneva, according to an opposition source who participated in the talks.
The group formed a new 50-member High Negotiations Committee (HNC), 11 of whom will be chosen to participate in the U.N. peace talks in Geneva next week, said Ahmed Ramadan, the head of the press department at the Syrian National Coalition, which took part in the Riyadh meeting.
"They will include members of the Cairo and Moscow platforms," Ramadan told dpa by phone from Saudi Arabia, a reference to different Syrian opposition groups with diverging opinions.
Another opposition member, Bassma Kodmani, said that the "Moscow [opposition] group took part in the Riyadh" meeting, where they stressed that they are committed to being in one delegation with other opposition groups.
The meeting in Riyadh continues on Friday, with a goal of finalizing names of representatives to the delegation and the new committee, opposition sources said.
The approximately 150 delegates gathering in Saudi Arabia since Wednesday reiterated that a solution to Syria's war, now in its seventh year, can only be achieved with the departure of Syrian regime leader Bashar Assad at the start of the transitional period.
Opposition groups have been divided by regional rivalries, as Russia backs Assad, while Turkey and other regional powers back different opposition groups.
