The two had a call on Thursday at the conclusion of Thomas-Greenfield's trip to Turkey.
"Ambassador Thomas-Greenfield also expressed U.S. opposition to renewed military operations in northern Syria, which could lead to additional population displacement, risk further destabilising the fragile situation on the ground, and undermine international coalition efforts to defeat ISIS," US Mission to the UN spokeswoman Olivia Dalton said.
On 23 May, Turkish President Recep Tayyip Erdogan said his country would soon start a new military operation into northern Syria against Kurdish militias who Ankara views as terrorist groups.
*Daesh (IS/ISIS/ISIL) is a terrorist organisation banned in Russia.