(Adds details on Pentagon not considering Turkey working group)
By Mike Stone
WASHINGTON, April 4 (Reuters) - A Lockheed Martin-made F-35 fighter jet for Turkey arrived on Wednesday at a military training facility in Arizona, an Air Force official said on Thursday, amid a dispute over Ankara's planned purchase of a Russian missile defense system.
Earlier this week, Reuters reported that the United States halted delivery of equipment related to the stealth F-35 fighter aircraft to Turkey because of concern the NATO ally’s planned purchase of the Russian system would compromise the security of the jet, the most advanced U.S. fighter aircraft.
A second jet is scheduled to arrive at Luke Air Force Base on Friday, the Air Force official said. Two Turkish F-35 jets are already at the base.
Pentagon spokesman Charlie Summers told reporters on Thursday: "The training (for pilots) will continue at Luke Air Force Base."
Turkish President Tayyip Erdogan has refused to back down from Ankara's planned purchase of a Russian S-400 missile defense system.
The United States and other NATO allies that own F-35s fear the radar on the system will learn how to spot and track the jet, making it less able to evade Russian weapons.
In an attempt to persuade Turkey to drop its plans to buy the S-400, the United States offered the pricier American-made Patriot anti-missile system in a discounted deal that expired at the end of March. Turkey has shown interest in the Patriot system, but not at the expense of abandoning the S-400.
Turkey has engaged with U.S. negotiators in recent days about buying the Patriot system, a person familiar with the matter said on condition of anonymity. The system is made by Raytheon Co.
Turkish Foreign Minister Mevlut Cavusoglu said on Wednesday that Turkey had proposed to the United States that they form a working group to determine that Russian S-400 missile defense systems do not pose a threat to U.S. or NATO military equipment.
On Thursday, the Pentagon said it was not considering a technical working group and that it was not necessary at this stage.
(Reporting by Mike Stone; Additional reporting by Idrees Ali in Washington; Editing by Phil Berlowitz and Peter Cooney)