Despite fierce opposition from NATO ally Turkey, the White House has approved supplying arms to Kurdish YPG fighters to support an operation to retake the Syrian city of Raqqa from Islamic State, a U.S. official told Reuters on Tuesday.

The official, who spoke on condition of anonymity, did not disclose how soon arms would start being delivered to the Kurdish fighters, who Ankara sees as an extension of PKK militia waging an insurgency on Turkish soil.