"We are concerned about the situation north of Aleppo and are working to de-escalate tensions on all sides," Kirby said.
He added that Washington urged Syrian Kurdish People's Protection Units (YPG) and affiliated forces against taking advantage "of a confused situation by seizing new territory."
"We have also seen reports of artillery fire from the Turkish side of the border and urged Turkey to cease such fires," Kirby stressed.
The spokesman argued that Ankara and YPG "share a serious threat" from the Islamic State, encouraging them to focus on anti-Daesh efforts and "work towards a cessation of hostilities."
Kurdish self-defense units claimed earlier that Turkish artillery forces shelled the recently captured Minnigh airbase in Aleppo, which Turkish Prime Minister Ahmet Davutoglu said was carried out in retaliation.