The U.S. and Turkey have reached an understanding meant to assure the Ankara government that plans to drive Islamic State militants from a proposed safe zone in northern Syria won’t clear the way for Kurdish fighters to move in.

Officials from both countries on Monday disclosed details of the discussions that grew out of Turkey’s recent decision to step up its cooperation with the U.S. in the fight against Islamic State.

The U.S.-led coalition fighting the extremist group has conducted numerous airstrikes over the past year to back the Kurdish YPG militia in northern Syria, which has proved to be the most effective ground force fighting Islamic State. […]