US Assistant Secretary of Defense Ellen M. Lord said that if Turkey does not give up on July 31 the purchase of the Russian S-400, the Turkish pilots currently trained in the US on F-35 aircraft will be expelled, Turkish manufacturer of pieces for the aircraft "F-35", according to the network was quoted by Al Arabiya Net.
The US official justified the warning that Turkey sent troops to Russia to train on the use of the S-400 missiles.
Acting US Defense Secretary Patrick Shanahan said he had sent a letter to his Turkish counterpart Khulosi Akar to inform him of his decisions and said the US offer on the Patriot was "very tempting."
The Pentagon has informed Turkey that it intends to cancel the recent purchase of F-35 fighter jets if the Turkish government goes ahead with the purchase of Russian missile defense system.
Shanahan sent a letter to Turkey that all Turkish pilots' training on this type of aircraft would be completed by July 31.
All Turkish military personnel associated with the F-35 aircraft program must leave the United States by the end of that month.
According to Shanahan's letter to Turkish Defense Minister Khulosi Akar, Turkey will not be allowed to receive the last batch of F-35 aircraft it had purchased, including four aircraft. The letter is the latest in a continuing dispute over Turkey's decision to buy the Russian S-400.
In a strongly worded two-page letter, Shanahan warned that Turkey's purchase of the Russian S-400 system could disrupt future relations between the United States and Turkey, a vital partner of Washington and a base for US combat operations, including in Syria.
"Buying Turkey for the S-400 will hamper your nation's ability to strengthen or maintain cooperation with the United States and within NATO," Shanahan told Khulosi Akar.
He added that the purchase of the Russian system "will lead to the adoption of a strategic and economic Turkey excessive to Russia."
He also warned that his decision to end Turkey's participation in the F-35 program could be followed by other US actions, adding that members of Congress supported sanctions against the Turks.
Shanahan and other US defense officials confirmed that these decisions were irreversible and relations could return to normal if Turkey gave up the Russian system.
Washington has repeatedly warned Ankara that the Russian system is a threat to the F-35.