The Pentagon has warned Turkey not to buy Russia's S-400 anti-aircraft missile system by July 31, or the NATO ally will no longer allow the highly developed F-35 fighter to buy or participate in any aspects of the program.
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"While we try to maintain our esteemed relationship, Turkey will not receive the F-35 if Turkey takes over the S-400," said Defense Secretary Patrick Shanahan in a letter to Turkish Defense Minister Hulusi Akar. "You still have the option to change course on the S-400."
Shanahan warned Akar that the United States had devised a plan to end Turkey's participation in the F-35 program by July 31
The United States wants Turkey to buy Patriot missile defense systems instead of the S-400 made in Russia. However, the Turkish leaders are firmly convinced that they prefer the Russian missile system, which they claim is significantly better than the American one.
US officials, however, fear the most that Russia could use the missile defense system to identify the stealth fighter's capabilities and potential vulnerabilities, in particular a radar profile that could identify the stealth fighter. These concerns are why US officials said the two systems were "incompatible."
"We do not want to keep the F-35 near the S-400 for a long time because it's understandable. The profile of the F-35 on this particular piece of equipment," said Ellen Lord, Undersecretary for Procurement and Sustainability , on Friday to reporters.
In addition to the non-delivery of the four F-35 aircraft Turkey already owns, Shanahan said that no other Turkish pilots would be trained in the US after 31 July. By that date, many Turkish pilots trained at Luke Air Force Base, Arizona, will have completed their courses before leaving the US.
The US decision could also have economic repercussions in Turkey, where more than 900 parts of the F-35 will be built under the original international consortium agreement for American allies to develop the F-35.
Approximately 400 of these parts, located in the landing gear and in the central fuselage of the aircraft, are manufactured exclusively by Turkish manufacturers.
Lord said the Pentagon is already taking steps to find alternative manufacturing facilities in other countries by early 2020.
The Pentagon's position seems to have been tightened by Turkey's recent confirmation that military personnel had already been sent to Russia to train the S-400 systems.