At least 13 countries are interested in buying a Russian missile system instead of platforms made by US companies, despite the threat of sanctions

One of the people, who declined to be named, said that Saudi Arabia, Qatar, Algeria, Morocco, Egypt, Vietnam, and Iraq have all discussed buying the S-400 missile system from Russia. However, the U.S. expects that a handful of countries will fold to diplomatic pressure.

China, India and Turkey have already signed purchase agreements with the Kremlin. China, which is embroiled in a trade battle with the U.S., is in the middle of receiving their final shipment of the S-400 system.

“Russia appears to be using air defense sales within much bigger political and economic frameworks,” Karako said. “In some cases, the purchase of S-400 looks a bit like what the ancient Romans called tribute.”