President Donald Trump has approved a plan to directly arm Kurdish forces fighting in Syria as part of a U.S. military plan to capture Raqqa, the Syrian city that is the Islamic State's de facto capital, the Pentagon said on Tuesday.

Pentagon spokeswoman Dana White said the president made the decision Monday and described the Kurdish People's Protection Units, or YPG, as “the only force on the ground that can successfully seize Raqqa in the near future.”

The decision, first reported by NBC, is sure to enrage Turkey, the NATO ally that views the YPG as a threat.