BUCHAREST, Romania (AP) — Romania's defense ministry confirms it has paid for three air-and-missile defense systems from the United States for its long-term defense strategy.

Defense Minister Mihai Fifor said Friday that the units, purchased this week, were in addition to a $3.9 billion military contract that Romania signed with the U.S. in 2017 for other Patriot missiles. The amount Romania paid was not available.

Mike Ellison, an official with Raytheon, which makes the Patriot missiles, said: "Romania is purchasing the most advanced, capable, cutting-edge tactical ballistic missile defense system in the world."

The U.S., Germany, Greece, the Netherlands, Spain and Poland — all NATO members — and Sweden, which is not — all have Patriot defense systems.

The purchase is part of Romania's strategic partnership with the U.S. The missiles are expected to become operational by 2020.