Updated

The foreign ministers of Russia, Iran and Turkey agreed Tuesday to facilitate convening the first session of a committee to draft a new Syrian constitution early next year, saying they hoped it will lead to the launch of a "viable and lasting" peace process.

In a joint statement read out by Russian Foreign Minister Sergei Lavrov, they said the work of the committee should be governed by a "sense of compromise and constructive engagement."

But U.N. Special Envoy for Syria Staffan de Mistura said "there is an extra mile to go in the marathon effort" to ensure a credible, balanced and inclusive constitutional committee. He refused to elaborate in his comments to reporters in Geneva following the meeting.

De Mistura, who is stepping down on Dec. 31, is scheduled to brief the Security Council on Thursday.

The 150-member committee, which has been a year in the making, is intended to represent the government, the opposition and civil society and is seen by the U.N. and U.S. as key to holding free elections and ending the seven-year civil war that has killed more than 450,000 people.

The U.N. Syria envoy was authorized to put together such a committee at a Russian-hosted peace conference in the Black Sea resort of Sochi on Jan. 30 but its formation has been hindered by disagreements and the U.N. has accused the Syrian government of blocking efforts to draft a new constitution.

At issue is the 50-member delegation representing civil society, experts, independents, tribal leaders and women which the government has been objecting to. There is already agreement on the 50-member delegation from the government and the 50-member delegation from the opposition.

"Slowly, we are reaching a conclusion," said Turkish Foreign Minister Mevlut Cavusoglu, suggesting there were still disagreements over which civil society groups would participate.

"We have reached an important step in our work toward the Syrian constitutional committee," he told reporters.

The Damascus government has previously told the U.N. envoy the constitution is a "sovereign" matter and that Damascus will not allow any foreign meddling in it.

The opposition has called for a new constitution that would allow for a political transition away from the Assad family's decades of rule. But after a string of major victories, the government shows little interest in making any concessions and has said it will only accept amendments to the current constitution.

On Monday, Syria's Foreign Minister Walid al-Moallem said that it's premature to talk about the start of the constitutional committee's work "due to the attempt of some western countries to intervene in its work."

___

Associated Press writers Suzan Fraser in Ankara, Turkey and Zeina Karam in Beirut contributed reporting