Erdogan says Turkey tested Russian S-400s, shrugs off U.S. objections

Turkish President Tayyip Erdogan confirmed on Friday that Turkey had been testing the S-400 air defence systems that it bought from Russia and said U.S. objections on the issue did not matter.Washington says Ankara's purchase of the Russian systems compromises NATO defences, and has threatened sanctions.An apparent firing test of S-400s test last week prompted a furious response from the U.S. State Department and the Pentagon.