The three states agreed to establish a constitutional committee during the Syrian National Dialogue Congress on January 30 in the Russian resort city of Sochi, TRT World reported.
De Mistura is meeting with the guarantor countries of the Astana process — Turkey, Russia, and Iran. The two-day meeting began on Monday.
On Friday, he will meet with officials from Egypt, France, Germany, Jordan, Saudi Arabia, UK, and US.
Talks on Monday was closed to press, while today’s meeting will be official and open to media.
The final declaration of the Syria summit held by the guarantor countries in Russia in July highlighted the establishment of a constitutional committee.
On July 5, the Syrian Negotiation Commission submitted a list of 50 candidates to represent the Syrian opposition in the constitutional committee to de Mistura, according to the Turkish Foreign Ministry.
Turkish President Recep Tayyip Erdogan emphasized the significance of forming a constitutional committee following a trilateral meeting with his Russian and Iranian counterparts in Tehran last week.
“Representatives of the three guarantor countries will meet again in Geneva with the UN’s Secretary-General’s special envoy on Syria in the coming days," Erdogan said on Friday in Tehran.
“The formation process of a constitutional committee will be discussed, and we can say that the preparations have come to the last stage,” he added.
Iranian President Hassan Rouhani, Russian President Vladimir Putin and Erdogan met in Tehran on Friday to discuss the future of Syria after the summit affirming that the Syrian conflict can only end through a "negotiated political process."
Russian President Vladimir Putin had also agreed to help in establishing the committee.
The meeting held under the UN umbrella to end the seven-year-old war in Syria consists of four titles including transition, Constitution, elections and the fight against terrorism.