The representatives of guarantor countries -- Turkey, Russia and Iran -- met UN Special Envoy to Syria Staffan de Mistura on Sept. 10-11 in Geneva.
"During the meeting, they discussed the formation of a constitutional committee and its codes of practice which constitute an important step in the struggle of finding a political solution to the Syrian crisis," the Turkish Foreign Ministry said in a statement on Tuesday.
The ministry said an agreement in principle, regarding the lists that were proposed by the Syrian regime and opposition, was discussed. Also consultation was held on the formation of a third civil society group.
It added meetings between the Astana guarantor states will continue.
Deputy Foreign Minister Sedat Onal represented Turkey during the meetings.
De Mistura will meet officials from Egypt, France, Germany, Jordan, Saudi Arabia, the U.K., and the U.S.
On Sept. 7, Turkish President Recep Tayyip Erdogan, his Russian counterpart Vladimir Putin and Iran's Hassan Rouhani held a trilateral meeting on Syria in the Iranian capital Tehran.
In a joint statement, the leaders reaffirmed their resolve to continue joint efforts aimed at advancing the Syrian-led and Syrian-owned process for reaching a political settlement and reiterated their commitment to help establish and launch the work of the constitutional committee.