The United States has halted delivery of equipment related to the stealthy F-35 fighter aircraft to Turkey, marking the first concrete U.S. step to block delivery of the jet to the NATO ally in light of Ankara's planned purchase of a Russian missile defense system.

U.S. officials told their Turkish counterparts they will not receive further shipments of F-35 related equipment needed to prepare for the arrival of the stealthy jet, two sources familiar with the situation said Monday.

The Pentagon confirmed the report that the equipment delivery had been stopped.