US to Turkey: No F-35 only if it buys Patriot missiles and not S-400
The US concerned for compromise of F-35’s security if Turkey buys the S-400 missile system
U.S.-Turkey relations headed toward perfect storm
Any country that attempted to buy S-400 systems would face sanctions, but the sanctions to be imposed on Ankara will be much more severe
Replacing Turkey in NATO
Turkey is on the way out and it doesn't seem to care...