The U.S. has warned its allies against buying Russian defense systems after Turkey, whose President Recep Tayyip Erdogan is photographed here this month in Ankara, made such a purchase. Photo by EPA-EFE/STR

Aug. 24 (UPI) -- The U.S. would consider implementing sanctions on any ally that buys a Russian air defense system, as Turkey has done, State Department spokeswoman Heather Nauert said.

The recent decline in U.S.-Turkish relations, caused in part by Turkey's detention of an American pastor on espionage and terrorism charges, also includes the Turkish purchase of the Russian S-400 air defense system. The S-400 is not compatible with systems used by Turkey, the United States and other NATO countries.


In a Thursday press briefing, Nauert said the U.S. could implement more sanctions against Turkey, and warned other NATO countries that sanctions could follow if they consider similar deals.

"It goes against our policy to have a NATO ally such as Turkey use an S-400 system. Part of the problem with that, it is -- that it is not interoperable with other NATO systems," she said. "And so we are against the -- having some of our partners and allies around the world potentially purchase S-400s."

When asked if such a purchase, by Turkey or any other country, would trigger Countering America's Adversaries Through Sanctions Act economic sanctions by the United States, Nauert added, "I'm not going to get into that, but we have made very clear what could trigger sanctions for other countries and entities around the world."

The U.S. has threatened to cancel a contract for the sale of F-35 stealth fighter planes to Turkey over its purchase of the Russian system, Russian state-run Sputnik News reported. Turkish Defense Minister Neurettin Canikli referred to the threats as blackmail.

The S-400 system will be delivered to Turkey in 2019, a year ahead of schedule, the Russian defense exporter Rosoboronexpoert announced earlier this week.

Washington is also pressuring India to abandon its planned purchase of elements of the S-400 system in a $5.7 billion deal, the state-run Russian news website RT reported on Friday.