Correction: 31/01/2018: A previous version of this article erroneously stated that Maya Alrahbi is a spokesperson for the Syrian Negotiation Commission. She is in fact a consultant for the SNC.

Participants of a Russia-hosted conference for peace in Syria have agreed to set up a commission to rewrite the war-torn country's constitution.

Staffan de Mistura, United Nations Special Envoy for Syria, said on Tuesday that delegates at the two-day conference at the Black Sea resort of Sochi, agreed to include both government and opposition officials in the 150-member committee.

De Mistura said the final agreement on the committee would be reached in the UN-led diplomatic process in Geneva based on UN Security Council Resolution 2254 - which serves as a framework for political transition in Syria.

But the fate of President Bashar al-Assad, a key sticking point that has repeatedly caused ongoing negotiations to fail, was not mentioned in the final statement.

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Syria's major opposition groups, who boycotted the event, rejected the proposal.

The main opposition bloc - the Syrian Negotiation Commission (SNC) - accused Assad and Russia, Syria's principal ally, of continuing to use military might and showing no interest in entering into honest negotiations.

"We reject the establishment of any constitutional commission at this stage," said Maya Alrahibi, a consultant for the SNC.

Instead, the bloc wants the government and the opposition to set up a transitional governing body first, she told Al Jazeera.

"During this transitional stage inside Syria, a constitutional commission can be set up consisting of members selected to represent all of the Syrian people," she said.

"The constitutional commission will then draft a new constitution that shall be approved after putting it to a vote in a referendum that is conducted fairly and transparently."

Hisham Marwah, a lawyer for the Syrian Coalition, a Turkey-based opposition group, said a "neutral and safe environment" in Syria was required for the writing of and voting on a new constitution.

"We don't have that," he said. "There are tanks rolling in the streets in Syria right now."

He added that the Sochi agreement violated past UN resolutions as well as a plan for peace set out by the US, Russia, China, France and some Arab countries including Iraq, Kuwait and Qatar in 2012, all of which called for the establishment of an inclusive transitional governing body to reform the constitution.

"We must go through the process one step at a time, as stated in the Geneva communique and the UN resolutions," he said.

Without the opposition's buy-in, the Sochi agreement would not help end Syria's war, other analysts said.

Charles Lister, an analyst with the US-based Middle East Institute, said the conference was "Russia's way of showing that it can pull together the broad spectrum of pro-regime and accepting-of-the-regime political parties in Syria".

However, without the opposition's involvement in large numbers, "then we're not talking about negotiations, we're talking about discussions. We're not talking about results, we're talking about statements," he told Al Jazeera from Washington, DC.

"Until that changes, we're going to continue to watch many of these different kinds of conferences in different cities, and unfortunately the crisis in Syria will continue."

Additional reporting by Cilina Nasser .