"We hope that the decisions to be made today and finally the statement issued by the three countries, will pave the way for a good future for Syria.
"The future of Syria will not be in the hands of foreign forces and powers. The Syrian future is in the hands of the Syrian people," Rouhani said before leaving for Russia's coastal city of Sochi, according to Iranian presidency statement.
Rouhani, Turkish President Recep Tayyip Erdogan and Russia's Vladimir Putin will meet later Wednesday to discuss progress made in the Astana peace talks as well as the changes in de-escalation zones across Syria.
Turkey and Russia, together with Iran, are the guarantor countries which brokered a cease-fire in Syria in December 2016, leading to the Astana talks, which are running parallel to the Geneva talks.
Rouhani reminded Astana talks were held following the decision of the three countries, adding: "Achievements have been made in this regard, and today, a very important summit is being held in Sochi…".
He also said Iran seeks collaboration and not confrontation in the region.
"Unfortunately, it has been over six years now that our region has been plagued by insecurity, instability and destructive activities of terrorists," he added.
Rouhani said territorial integrity, national sovereignty and independence of Syria were "very important" for Iran.