Tens of thousands of people died because a safe zone was not implemented quickly enough in northern Syria, Turkish President Recep Tayyip Erdogan said Wednesday.

Erdogan made the comments during a joint press conference with U.S. President Donald Trump following four hours of bilateral meetings that also included a sit-down with Republican senators.

Turkey launched Operation Peace Spring on Oct. 9 to eliminate YPG/PKK terrorists from northern Syria east of the Euphrates River in order to secure Turkey’s borders, aid in the safe return of Syrian refugees and ensure Syria’s territorial integrity.

Read more: Erdogan: Thousands died from delay in Syrian safe zone