De Mistura is scheduled to arrive in Tehran on Sunday to exchange views with Iranian Foreign Minister Mohammad Javad Zarif and Deputy Foreign Minister for Arab and African Affairs Hossein Jaberi Ansari.
The sides will discuss the latest developments in the war-stricken country and the upcoming peace talks in Geneva, Switzerland.
Speaking at a news conference in Berlin on July 22, the UN official said there was determination to find a proper date for the resumption of the Syria peace talks.
"We are determined to actually look for a proper date in August for relaunching the intra-Syrian talks in Geneva," De Mistura said.
He expressed optimism that the results of talks between the US and Russia can be helpful in resolving the crisis in Syria, saying the two sides have agreed to take some "concrete steps" to restore peace to Syria.
The US and Russia are still divided over the future of Syrian President Bashar al-Assad. Washington insists that Assad must step down before any peace process can yield results, but Russia opposes the idea, arguing that the Syrian president is defending his country against terrorists.
Meanwhile, Russia’s Ambassador to the UN Alexey Borodavkin said on Thursday that the Syrian president had sent an invitation on July 24 to UN deputy dpecial envoy for Syria, Ramzy Ezzeldin Ramzy, who plans to visit Damascus on July 30 to “discuss ways of possible political settlement of the crisis in the country.”
He added that President Assad is “ready to consider" de Mistura's proposals on "normalizing the situation in the country.”
Syria has been gripped by foreign-backed militancy since March 2011. The UN special envoy for Syria estimates that over 400,000 people have been killed in the conflict.
The UN has stopped its official casualty count in Syria, citing its inability to verify the figures that it receives from various sources.