UPDATE 1-Turkish F-35 delivered to training base in Arizona, official says

A Lockheed Martin-made F-35 fighter jet for Turkey arrived on Wednesday at the training facility at Luke Air Force Base amid a dispute with the United States over its planned purchase of a Russian missile system, a Pentagon official said on Thursday. Earlier this week, Reuters reported that the United States halted delivery of equipment related to the stealthy F-35 fighter aircraft to Turkey. It marked 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.

This is the first of two jets expected to be delivered to the base this month. Two Turkish jets are already at the base. Turkish President Tayyip Erdogan has refused to back down from Ankara's planned purchase of a Russian S-400 missile defense system that the United States has said would compromise the security of F-35 aircraft.

The United States and other NATO allies that own F-35s fear the radar on the Russian S-400 missile system will learn how to spot and track the jet, making it less able to evade Russian weapons. (Reporting by Mike Stone in Washington Editing by Chizu Nomiyama and Phil Berlowitz)