"The @OSCE Co-Chairs will meet in Vienna on Monday and convene the Minsk Group on Tuesday to address violence in Nagorno-#Karabakh," Warlick wrote in his Twitter account.
Earlier on Saturday, the Minsk Group expressed concern over resumed clashes in the contested region. The Russian Foreign Ministry announced holding consultations with the group on conflict settlement in the self-declared Nagorno-Karabakh Republic.
The Minsk Group is co-chaired by ambassadors from Russia, the United States and France.
The conflict in Nagorno-Karabakh began in 1988, when the Armenian-dominated autonomous region sought to secede from the Azerbaijan Soviet Socialist Republic, before proclaiming independence after the Soviet Union's collapse in 1991. In September 2015, the conflict escalated, with the sides blaming each other for violating the truce.