Turkey is sticking to its guns over its controversial purchase of Russian made S-400 missile air defense systems. Increasing domestic skepticism regarding the reasons for the purchase has also not deterred Ankara, which is generally averse to political compromise.

The US sanctions slapped on Turkey Dec. 15 under the Countering America's Adversaries through Sanctions Act (CATSAA) have merely hardened Ankara’s line.

Washington says the Russian systems threaten NATO’s state-of-the-art F-35 fighter jets, which Turkey was also in line to get, and wants Ankara to ensure that the S-400s will not be activated. Turkey, however, went ahead and conducted a trial run in October in the Black Sea city of Sinop. The move crystallized bipartisan anger at Turkey in the US Congress, which pressed for the CATSAA sanctions to be imposed.

President Recep Tayyip Erdogan and members of his government continue to stress that Turkey will not bow to pressure from the United States or Europe over the matter, and Foreign Minister Mevlut Cavusoglu has announced that retaliatory steps against Washington are in the pipeline.