ABOARD US MILITARY AIRCRAFT - U.S. service members will begin training Turkish forces for joint patrols near the volatile Syrian city of Manbij within the next three days, according to U.S. Secretary of Defense Jim Mattis.

“I would say within 72 hours actually. Very soon, could be sooner,” Mattis told reporters aboard a U.S. aircraft Thursday.

Mattis said U.S. training gear and equipment, along with the training officers, were now in Turkey.

The training is needed before U.S. and Turkish forces operating near Manbij can combine their patrols.

Right now, the two forces are conducting “coordinated but independent” patrols, according to the Pentagon.

It is unclear when U.S. and Turkish forces would start conducting the joint patrols in Syria once training of Turkey’s troops is complete.

The city of Manbij houses Kurdish militia fighters. Washington supports the Kurdish fighters there, while Ankara says they are anti-Turkey terrorists.

The Pentagon says the purpose of the patrols are to support “long-term security in Manbij” and uphold its commitments to NATO-ally Turkey.