According to some sources Beijing expressed interest to acquire Russian S-400 counter-missile system. To date the Chinese use the components of the S-300 system but are said to be willing to enter closer co-operation on military and technological levels which would eventually lead to implementation of the S-400′s in a near future. Russia is currently developing its replacement, i.e. S-500 which is about to enter the line around 2020.
While China could become a major customer for the Russian air defense system, negotiations will be tough, since the Russians are becoming more protective on intellectual property and reverse engineering, as practiced by China in the past. A planned procurement of Su-35 that seemed a done deal has recently collapsed after the Russians refused to compromise on these demands.