The United States criticized clashes between Turkish forces and some opposition groups in northern Syria on Aug. 29 as “unacceptable” and called on all armed actors in the fighting to stand down and focus on the fight against Islamic State of Iraq and the Levant (ISIL), the Hurriyet Daily News reports.

“We want to make clear that we find these clashes – in areas where ISIL is not located – unacceptable and a source of deep concern,” Brett McGurk, the special presidential envoy for the coalition to counter ISIL, said on his official Twitter account, citing a defense department statement.

“We call on all armed actors to stand down… the U.S. is actively engaged to facilitate such deconfliction and unity of focus on ISIL, which remains a lethal and common threat.”

Turkey and its Syrian rebel allies seized territory controlled by Kurdish-aligned forces on Aug. 29, the fifth day of a cross-border campaign.

Turkish officials say their goal in Syria is to drive out ISIL but also to ensure the People’s Protection Units (YPG) militia, the military wing of the Democratic Union Party (PYD) in Syria, which Ankara says directly linked to the outlawed Kurdistan Workers’ Party (PKK), do not expand the territory they already control along Turkey’s border.

The YPG fighters are backed by the United States in the fight against ISIL in Syria.