The U.S. government formally notified Congress of a proposed $700 million sale of GE Aerospace F110 engines to Turkey.

The agreement covers dozens of engines for the TAI Kaan, Turkey’s domestically developed fifth-generation fighter jet.

GE engines will power initial production aircraft until a Turkish-made engine is ready for deployment.

This diplomatic step occurs ahead of a scheduled NATO summit in Ankara.

U.S. lawmakers previously voiced concerns over Turkey’s purchase of the Russian S-400 missile system.