The Russians gain income, security and prestige from such sales.

Axar.az reports that the statement came from US Defense Department spokesman Colonel Thomas Campbell.

He said Russian-made S-400s posed a greater threat to NATO and the United States than S-300s.

"The S-400 is a greater threat to NATO and the United States than the old systems. We urge Turkey not to hold this system. Turkey is a valuable NATO ally, but this is not in line with Turkey's commitments as a US and NATO ally."

Although Greece has S-300 systems, NATO and the United States have not objected.