De Mistura made the announcement on the fourth day of the current talks on Sunday.
He added that by the end of the current session both the Syrian government and the foreign-backed militant groups “would have a deeper shared understanding of how we can proceed in future rounds."
Meanwhile, the main Syrian opposition group has accused the Syrian government of trying to stall the talks, after Syria’s Ambassador to the UN Bashar al-Ja’afari called on all parties to condemn a deadly attack in Homs or be considered "accomplices of terrorism."
On Saturday, simultaneous bombings targeted separate areas across the western city of Homs -- which is largely under government control -- claiming the lives of over 50 people. The Jabhat Fateh al-Sham terrorist group, formerly known as al-Nusra Front, claimed responsibility for the attacks.