Raytheon Company did not disclose details of the deal but indicated that the letter of purchase paves the way for negotiations with the Trump administration.
The Gulf country will use the system to upgrade its defense against ballistic missiles, cruise missiles, and manned and unmanned aircraft.
The small kingdom has been facing internal insurgency and threats from Iran-backed proxies in the region and at home.
In May the US administration indicated that it approved Bahrain’s procurement of the Patriot system at an estimated cost of $2.478 billion. The purchase covers 60 Patriot Advanced Capability-3 (PAC-3) Segment Enhancement missiles, 36 Patriot MIM-104E Guidance Enhanced Missiles (GEM-T), nine M903 Launching Stations, and other components, tools and test equipment.