U.S. officials urged Turkey to buy U.S. Patriot missiles, arguing the Russian system would be incompatible with NATO systems and expose the F-35s to possible Russian subterfuge.
Turkey, however, emphasized the S-400 would not be integrated into NATO systems and would not pose a threat to the alliance. It has urged the formation of a commission to clarify any technical issues, but the U.S. has failed to respond to Turkey’s proposal.
The U.S. threatened sanctions over the purchase, with Turkey responding that any sanctions would be met in kind.