"Our policy remains clear in that region: The only solution to this conflict is a negotiated settlement based on international law that includes adherence to the principles of non-use of force, territorial integrity, and self-determination," Nauert said on Thursday.
She pointed out that the United State was deeply concerned with the recent escalation of the conflict.
"The United States remains deeply concerned over Tuesday’s violations of the ceasefire in the Nagorno-Karabakh conflict that resulted in multiple civilian casualties, including possibly a two-year-old child. This happened near the line of contact. We wish to extend our heartfelt condolences to the families of those victims," Nauert said.
The spokesperson also called on the parties to the conflict to cease hostilities and to return to the negotiating table.
Azerbaijan's Armenian-dominated region of Nagorno-Karabakh proclaimed its independence in 1991, triggering a military conflict that led to Baku's loss of control over the region. The violence between Azerbaijani and Nagorno-Karabakh forces escalated on April 2, 2016, leading to multiple casualties. The sides agreed to a ceasefire on April 5, but clashes have continued.