"I think there is a high probability. They have an option, they have a right to implement it," Borisov told reporters, answering the question about the possible new contracts on deliveries of air defence systems to Turkey.
Moscow and Ankara signed a loan agreement for the delivery of S-400 systems in December 2017. The deliveries kicked off in mid-summer.
Earlier this week, a group of US senators submitted legislation known as the 'Turkey Sanctions Bill' proposing 'wide-ranging mandatory sanctions' against Turkey over its S-400 deal with Russia.
Turkey's purchase of Russia's S-400 prompted the US to suspend Ankara's participation in the F-35 joint strike fighter program. Washington is concerned about the Russian system sharing airspace with F-35 jets. However, Turkey says these concerns are unfounded and insists that its intention to possess the S-400 will not change and nor will its decision to take part in the F-35 program.