The following is attributable to Spokesperson John Kirby:
U.S. Secretary of State John Kerry called Turkish Foreign Minister Mevlut Cavusoglu today to convey his condolences regarding the recent terror attacks in Turkey. The Secretary also offered U.S. assistance to the investigation into the horrific murder of Russian Ambassador to Turkey Andrey Karlov. Secretary Kerry and Foreign Minister Cavusoglu also discussed the situation in Syria and the ongoing efforts to reach an immediate ceasefire, secure the prompt delivery of humanitarian assistance, and resume political talks to end the civil war.
Source: U.S. State Department.