The United States has notified Turkey that it is cancelling its purchase of F-35 fighter jets if the Turkish government goes ahead with the purchase of a Russia's S-400 missile defence system.
Acting US Defense Secretary Patrick Shanahan has sent a letter notifying Turkey that all training of Turkish pilots will also end 31st of July.
And all Turkish personnel connected to the F-35 programme must leave the country by the end of that month.
In his letter, Shanahan also warned Ankara that its deal with Moscow risked undermining its ties to NATO, hurting the Turkish economy and creating over-dependence on Russia.
Shanahan wrote that you still have the option to change course on the S-400 .