If US officials were to expel Turkey from the multinational group that builds the fifth-generation F-35 fighter jets, Turkish defense officials said they likely would pursue Russian fighter jet technology.

“We cannot afford to leave the F-35 not substituted,” a Turkish senior military officer told Defense news.

A Turkish defense procurement official said “geostrategic assessment” would make Russian options emerge as the natural first replacement. “Russian fighter technology would the first best choice if our American allies behaved in an un-allied way and questioned Turkey’s membership in the Joint Strike Fighter program,” he said.

Washington has threatened to expel Ankara from the multinational program if Turkey deploys the Russian-made S-400 missile system on its soil.