U.S.-Turkey relations have soured after Turkey purchased a Russian missile defense system, the first deliveries of which were made on Friday. The USA had warned Turkey not to buy the S-400 missile defense equipment from Russia. The USA and Turkey are both allies in NATO - a defense organization created to counter any possible military aggression by Russia. NATO consists of 29 North American and European nations. The USA has the biggest military in NATO. Turkey has recently been establishing closer ties with Russia. This has caused security concerns for the USA.
The U.S. warned Turkey it would face economic sanctions if it installed the S-400 system. It also said Turkey would not be part of the USA's high-tech F-35 fighter jet programme. The U.S. wants Turkey to buy its Patriot missile defense system. U.S. officials say the Russian system is incompatible with NATO systems and would risk F-35 fighter jets to possible Russian trickery. Turkey has no plans to integrate the S-400 with NATO systems and says it would pose no threat to NATO. Turkey said the purchase of the S-400 did not mean it is seeking "alternatives" in its relations with the West.