Russian President Vladimir Putin, right, listens to Syrian President Bashar Assad during their meeting at the Kremlin in Moscow, Russia, Wednesday, March 15, 2023. AP
His comments come one day after he met Russian President Vladimir Putin, who is seeking to repair ties between Erdogan and Assad severed after the 2011 Syrian war.
"(Any meeting) is linked to our reaching the point when Turkey is ready -- fully and without any uncertainty -- for a complete withdrawal from Syrian territory," Assad told Russia's state-run RIA-Novosti news agency.
The Syrian leader, who arrived in Moscow on Tuesday, demanded that Turkey end its "support for terrorism" alongside a withdrawal, a reference to rebel groups that control regions of northern Syria and oppose Damascus.
"This is the only way in which my meeting with Erdogan could take place," Assad was cited as saying.
"What significance would any kind of meeting have -- and why organise it -- if it doesn't lead to a conclusion of the war in Syria?" he added.
Erdogan and Assad had amicable relations in the 2000s after years of tensions between their countries following the breakup of the Ottoman Empire.
But Syria's civil war, which has left some 500,000 people dead and displaced millions, strained relations between Damascus and Ankara, which has long supported rebel groups opposed to Assad.
Diplomats from Iran, Russia, Turkey and Syria are due to meet in Moscow this week to pave the way for a foreign ministers' meeting, according to Turkish media.