U.S State Department spokesperson made a statement late Saturday after Turkish troops shelled Kurdish positions in Syria in retaliation.
Kirby warned the Kurdish Democratic Union Party's (PYD) armed wing People's Protection Units (YPG) to stop exploiting the chaotic situation in Syria to obtain control over new areas.
"We have urged Syrian Kurdish and other forces affiliated with the YPG not to take advantage of a confused situation by seizing new territory," Kirby said in the statement.
John Kirby urged both Turkey and Syrian Kurds to step back, saying they should focus instead on tackling the "common threat" of Daesh militants who control large parts of Syria.
"We are concerned about the situation north of Aleppo and are working to de-escalate tensions on all sides," State Department spokesman John Kirby said in a statement.
"We have also seen reports of artillery fire from the Turkish side of the border and urged Turkey to cease such fires," he added.
Turkish military has shelled YPG terrorist targets near the town of Azaz in northern Syria. Reports say Turkey has hit areas belonging to the YPG, which has encircled the Azaz town of Aleppo. Troops are using Turkish-made Fırtına howitzers, according to reports.
Turkey's military campaign came as a response to increasing assaults on Azaz in the last 48 hours. PYD-linked armed groups have entrenched assaults in Aleppo's town with the help of Russian air forces.
