The United States has switched on an 800-million-dollar missile shield in southern Romania. It sees the system as vital to defend itself and Europe.

US and NATO officials say the ballistic missile defense site is capable of shooting down rockets from countries such as Iran, that Washington says could one day reach major European cities. But US Deputy Defense Secretary Robert Work said the shield would not be used against any future Russian missile threat.

Photo taken on May 12, 2016 shows the AEGIS Ashore missile defense system at Deveselu military base, southwest of Bucharest, Romania. The U.S. AEGIS Ashore missile defense system in Romania is certified for operations, NATO Secretary General Jens Stoltenberg announced Thursday. (Xinhua/Lin Huifen)

The system is at the remote Deveselu air base. When complete, the defensive umbrella will stretch from Greenland to the Azores. The full shield also includes ships and radars across Europe.