Turkey is ready to take over security in Syria’s Manbij without delay, President Recep Tayyip Erdogan told U.S. President Donald Trump in a telephone call on Sunday, the Turkish presidency said.

Erdogan said an attack that left four U.S. personnel dead last week in Manbij was an act of provocation aimed at affecting Trump’s decision last month to withdraw U.S. troops from Syria, Reuters reports.

Manbij is controlled by a militia allied to the U.S.-backed Kurdish YPG, who last month invited Syrian President Bashar Assad into the area around the town to forestall a potential Turkish assault.