MOSCOW, August 16. /TASS/. Active work is in progress for the supply of a second batch of air defense systems S-400 to Turkey under the previously concluded contract, Russian presidential aide, Yury Ushakov, told the media.

"Active work is underway for the supply of a second batch of S-400," he said adding that he was referring to the previously concluded agreements. As far as military-technical cooperation is concerned, negotiations are being conducted on a wide range of issues.

"I would not say anything concrete about planes," Ushakov said, when asked if Turkey put the possibility of purchasing Sukhoi-35 planes on the agenda.