Russia, Turkey and Iran pledged Tuesday in Kazakhstan to bring the Syrian regime and its opponents together for a "congress" to help nudge peace efforts towards a more lasting political settlement.
A joint statement released by Russia and Iran, who support the regime, and Turkey, which backs the rebels, referred to an "initiative of Russia" to put Syrian government representatives and opposition groups face-to-face.
A statement on the Russian foreign ministry website on Tuesday listed 33 Syrian organisations invited to a "Congress of Syrian National Dialogue" in the Russian city of Sochi on November 18.
The proposal was one of the few notable outcomes from the seventh round of talks on Syria held in the Kazakh capital Astana, which are widely viewed as Moscow's attempt to stamp its imprint on a settlement for Syria.
Russia's chief negotiator for Syria, Aleksandr Lavrentyev, urged opposition factions to "participate and present their positions" in the meeting that he said would touch on constitutional reform.
But Lavrentyev could not confirm that the United Nations and its Syria envoy Staffan de Mistura would take part in the Sochi meeting, despite continuing negotiations.
"We want to emphasise that this event should be part of the international community's efforts to find effective mechanisms for political settlement," Lavrentyev said.
But representatives of the Syrian opposition in Astana cast doubt on the plan.
Yehya al-Aridi, a spokesman for the Syrian opposition, called the suggestion "a jump in the air to another place" and said the congress risked sending "a fake message" on Syria.
"We told Russia, 'First stop killing our children'," said another rebel representative, Yasser Abdelrahim, who brandished what appeared to be photos of dead children at the plenary session in Astana.
The Astana talks that began in January have run parallel to negotiations taking place in Geneva with the backing of the United Nations, and the congress plan appears to be Moscow's attempt to force the pace in a bid for a political settlement.
Speaking Tuesday, Russian Foreign Minister Sergei Lavrov credited the Astana negotiations with waking up a "dozing" Geneva process.
Nevertheless, Lavrov said there had been a recent "slowing in the efforts made as part of the Geneva process."
"We believe it is necessary not to hesitate but rather to seize the initiative," he said.
Russian President Vladimir Putin will travel to Tehran on Wednesday for talks with Iranian President Hassan Rouhani, the Kremlin has confirmed.
Recent rounds of talks in Kazakhstan have focused on ironing out the details of a Russia-led plan establishing four "de-escalation" zones in Syria.
The plan was first tabled in Astana in May to minimise fighting between government forces and moderate rebel factions and improve civilians' access to aid.
The fourth and final zone to be established was the thorniest, taking in the northern province of Idlib where Iran and Turkey are viewed as having competing interests.
In Astana, Syrian government negotiator Bashar al-Jaafari denounced Turkey's presence in the province and accused Ankara of cooperating with extremist groups.
"We have emphasised that we see the presence of Turkish armed forces in Idlib as an act of occupation," al-Jaafari said.
The zones were initially credited for bringing about a significant reduction in fighting.
But international aid organisations say they are failing to curb a recent uptick in violence which has significantly worsened humanitarian conditions in Syria.
The International Rescue Committee in the Middle East released a statement Monday that said civilian safety had "not improved with the establishment of these so-called de-escalation areas."
"Air attacks, as well as the impact of fighting between groups, has made it harder for food and medicine to get in," said Tom Garofalo, director of the group's public affairs.
Lavrentyev had described the situation in Eastern Ghouta as "satisfactory" on the first day of taks in Astana.
"Humanitarian aid is able to arrive," he said.
The multi-sided Syrian war that began with anti-government protests in March 2011 has claimed more than 330,000 lives.