Turkish and Iranian foreign ministers discussed initiatives to end the Syrian conflict in a phone call on Sunday, Turkey’s state-run Anadolu news agency reported.

Turkish Foreign Minister Mevlüt Çavuşoğlu and his Iranian counterpart Mohammad Javad Zarif discussed the establishment of a committee including Syrian opposition and government figures to write a new Syrian constitution, Anadolu reported, citing diplomatic sources.

The pair also spoke about the Astana peace process, which was launched by Iran, Russia and Turkey in January 2017.

Iran and Russia have helped their ally, Syrian President Bashar Assad, defeat opposition forces throughout nearly all of Syria since then.

This year, Syrian government forces with Russian backing launched an attack on Idlib, the last province held by opposition fighters, including Turkish-backed rebels.

Syrian government and opposition representatives said they would take measures to protect civilians and Turkish soldiers stationed at observation posts in Idlib during the last round of the Astana peace talks on Aug. 2.

Over the next month, Assad’s forces pressed on with their advance in the province, driving thousands of displaced Syrians towards the border with Turkey.

Turkey backed the Syrian uprising in 2011 and is now host to more than 3.6 million registered Syrians who fled the conflict.