U.S. President Donald Trump told Turkish President Recep Tayyip Erdogan to curtail his country’s military operations in Syria’s Afrin and avoid risk of conflict with American forces, the White House said.

In a phone call on Wednesday, “President Trump relayed concerns that escalating violence in Afrin, Syria, risks undercutting our shared goals in Syria,” the White House said in a statement. “He urged Turkey to deescalate, limit its military actions, and avoid civilian casualties and increases to displaced persons and refugees.”

Erdogan seemed critical of Trump’s comments and asked the United States to halt weapons support to the Kurdish YPG militias in Syria, Erdogan’s office said.