Qatar is in the “advanced stage” of negotiating the purchase of Russia’s advanced S-400 anti-aircraft system. The long-range SAM missile weapon seems to be the latest fad in the Middle East after its Syria showcase. Doha’s negotiations with Moscow on the purchase of the S-400 system is “in the advanced stage,” Qatari Ambassador to Russia Fahad bin Mohammed Al-Attiyah told TASS news agency.