The United States has carried out a fresh delivery of ammunition to fighters from the Syrian Arab Coalition battling the Islamic State group in northern Syria, pushing ahead with a strategy that initially unnerved ally Turkey, a U.S. official said Sunday.

The delivery of ammunition represented only the second time the United States has moved to arm the Syrian Arab Coalition, a collection of about 10-12 groups numbering about 5,000 fighters. They are working with Kurds and others to claw back land from Islamic State militants.

In a shift in approach, the latest U.S. resupply operation was completed on Saturday by delivering the weaponry by land, the U.S. official said, speaking on condition of anonymity.