Representatives of Iran, Russia and Turkey met in Kazakhstan's capital Astana on Wednesday to discuss a crumbling 10-week-old truce in the rebel-held Syrian province of Idlib after confrontations between rebels and government early this week threatened to derail the agreement.
The formation of a committee to draft a new Syrian constitution does not seem to be on the official agenda for the two-day talks, although UN envoy to Syria Staffan de Mistura is expected to discuss the issue with the three guarantor countries of the Astana peace process.
The meeting is likely be Mr de Mistura's last engagement on the Syria conflict before stepping down next month, and he has said he would spare no efforts to secure an agreement on the constitution-drafting committee.
The plan to form a 150-member committee comprising representatives of the government, opposition and civil society has floundered since it was announced at a Russian-sponsored Syria summit in January.
Delegations from the Syrian government and opposition are also taking part in the Astana meeting — the eleventh since Moscow launched the alternative peace push in early 2017 that effectively sidelined UN-led negotiations in Geneva.
In addition to Idlib, the talks will focus on creating conditions for the return of refugees and internally displaced people, as well as post-conflict reconstruction, the Kazakh foreign ministry said.
The fragile truce in Idlib came under strain this week after Russia launched air raids on rebel positions in neighbouring Aleppo. It was the first such attack since Moscow and Ankara agreed in September to create a demilitarised zone in the area to prevent a full-scale government assault.
Sunday's air strikes came hours after the Syrian government accused rebels in Aleppo of launching a poison gas attack that reportedly injured more than 100 people.
Rebels and activists, however, dismissed the charges as a pretext to allow the Syrian government and its Russian backers to resume air strikes in violation of the Idlib deal.
The issue of refugee returns has also sparked controversy in recent weeks after reports surfaced that the Syrian government had arrested and killed a number of repatriates. Aid organisations and human rights groups repeated their warning against premature return, saying that conditions in Syria were not yet ripe for such a move.
Meanwhile, UN war crimes investigators on Wednesday called on Syria to provide information and medical records to families of people who died or were executed while in government custody.
"Most custodial deaths are thought to have occurred in places of detention run by Syrian intelligence or military agencies. The commission has not documented any instance, however, where bodies or personal belongings of the deceased were returned," the International Commission of Inquiry on Syria said in a report.
In nearly every case, death certificates for prisoners that were provided to families recorded the cause of death as a "heart attack" or "stroke", the independent panel led by Paulo Pinheiro said.
"Some individuals from the same geographic area share common death dates, possibly indicating group executions," it said.
The report comes in light of a recent move by the Syrian government to update official death records with the names of people who died in custody after the uprising against President Bashar Al Assad began in 2011.