The United States imposed long-anticipated sanctions on Turkey on Monday over Ankara’s acquisition of the Russian S-400 air defense systems, further complicating already strained ties between the two NATO allies. Turkey condemned the sanctions as a “grave mistake” and urged Washington to revise its “unjust decision.” Senior U.S. officials said in a call with reporters that Ankara’s purchase of the S-400s and its refusal to reverse its decision left the United States with no other choice. The sanctions, first reported by Reuters last week, target Turkey’s top defence procurement and development body Presidency of Defence Industries, its chairman Ismail Demir and three other employees. While limited to one company, they are still likely to weigh on the Turkish economy, analysts said, at a ti...