Kazakhstan says delegations from Iran, Russia and Turkey are arriving in Astana for a third round of talks to put an end to the conflict in Syria.
Kazakh Foreign Minister Kairat Abdrakhmanov said on Monday that delegations had already started arriving despite a request from Syrian militants to delay the meeting.
The third round of Astana talks is due to take place on March 14-15, with Iran, Russia and Turkey trying to shore up a ceasefire between the warring sides that was brokered in December.
Tehran-based media said the Iranian team had departed for Astana, headed by Deputy Foreign Minister for Arab and African Affairs Hossein Jaberi Ansari.
The first round of the Astana talks took place on January 23-24. The second round was held on February 15-16.
Last week, the militants called for the postponement of the process, saying they had to first make sure about Damascus and its allies’ adherence to the ceasefire.
On Monday, the French news agency AFP said an opposition delegation had told it that militant groups would not attend the negotiations.
"Rebel groups have decided not to participate in Astana," the agency quoted Osama Abu Zeid as saying.
one reason for the boycott was "unfulfilled pledges related to the cessation of hostilities."
"We decided not to participate in Astana because the reinforcement of the ceasefire was not implemented," said Ahmad Othman, commander of the Ankara-backed Sultan Murad militant group, according to AFP.
The Astana talks got off the ground after the negotiators successfully mediated an all-Syria ceasefire. The agreement was on the extension of a previous one bringing about a cessation of hostilities in the northwestern Syrian city of Aleppo.
The Syrian delegation will be headed once again by the country's representative to the UN Bashar al-Ja'afari, who has also led the government's representatives in parallel UN-backed talks in Geneva.
A fresh round of negotiations in Switzerland is set to begin on March 23 and will focus on governance, constitutional process, elections, counter-terrorism and possibly reconstruction.