Despite fierce opposition from NATO ally Turkey, U.S. President Donald Trump has approved supplying arms to Kurdish YPG fighters to support an operation to retake the Syrian city of Raqqa from Islamic State, U.S. officials said on Tuesday.

Ankara views the Kurdish YPG militia fighting within a larger U.S.-backed coalition as the Syrian extension of the Kurdish PKK militant group, which has fought an insurgency in Turkey’s southeast since 1984.

There was no immediate reaction from Turkey, whose president, Tayyip Erdogan, is expected to meet Trump later this month.

The Pentagon immediately sought to stress that it saw arming the Kurdish forces “as necessary to ensure a clear victory” in Raqqa, Islamic State’s de facto capital in Syria and a hub for planning the group’s attacks against the West.