MOSCOW     -    Russia and Turkey are holding talks about the possible sale of Russian-made Sukhoi SU-35 fighter jets to Turkey, but it is too early to talk about a concrete deal, RIA news agency cited a senior Russian official as saying on Friday. Turkey has been at odds with the United States over its purchase of Russian S-400 missile systems, which Washington says are not compatible with NATO defenses and poses a threat to Lockheed Martin’s F-35 ‘stealth’ fighter jets. The United States has also expelled Turkey from the F-35 program, but Ankara has so far dismissed the warnings.