In early July, Russian Deputy Foreign Minister Gennady Gatilov said Moscow was ready to host the third round of intra-Syrian talks.
"Minister Walid Muallem sent de Mistura an invitation to participate in the consultations," Haddad told RIA Novosti.
The ambassador added that the date of the meeting is yet to be determined.
On January 26-29, Moscow hosted the first round of talks between the representatives of the Syrian government and a number of opposition groups since January 2014, when a UN-backed conference on the Syrian conflict in Geneva failed to yield significant results.
Syria has been in a state of a civil war since the 2011 anti-government uprising. The country's authorities are fighting a number of rebel groups, including Islamic State extremists.
According to UN estimates, the conflict has claimed some 220,000 lives. As of July 2015, at least 7.6 million people have been internally displaced by the war.
