MOSCOW, MOSCOW (Reuters) - Russia and Saudi Arabia are on track to sign a contract on supplies of Russia s advanced S-400 air defense missiles to Riyadh, the Interfax news agency cited an aide to Russian President Vladimir Putin as saying on Friday.  The talks are ongoing now, the terms are being agreed,  the agency cited Vladimir Kozhin as saying. He said the contract could be signed  in the nearest time,  giving no further detail. 
Russia, Saudi Arabia close to sign S-400 missile deal: Ifax cites Putin aide