Spain's Rota naval base will host four U.S. ships deployed as part of NATO's missile-defense system, Spanish Prime Minister Jose Luis Rodriguez Zapatero said here Wednesday.

"Spain will receive this component of the system due to its geostrategic location and as a gateway to the Mediterranean," Zapatero said in a joint press conference with NATO Secretary-General Anders Fogh Rasmussen and U.S. Defense Secretary Leon Panetta.

Rota will serve as a base for U.S. ships and some 1,100 troops beginning in 2013 in a move Panetta termed critical to protecting Europe against the threat of ballistic missiles.

The U.S. ships, part of the initial deployment of a NATO-designed anti-missile shield, are equipped with radar and Aegis missile-intercept systems.

A land-based, anti-missile component will be added in the coming years as fruit of agreements Washington signed with Romania and Poland, which will host missile interceptors, and Turkey, where a sophisticated radar system is to be installed.

Zapatero told reporters Wednesday at NATO headquarters that the anti-missile shield is intended only as a deterrent and therefore is not a threat to anyone.

Plans for the defense shield, approved by NATO leaders last year in Lisbon as a response to potential threats from countries such as Iran, which currently has no missiles capable of reaching Europe, initially caused friction with Russia.

Moscow saw it as a threat and offered to help develop a joint anti-missile system, but the alliance rejected the offer and instead opted for two parallel defense mechanisms - Russia's and NATO's - that will cooperate and exchange information.

Spain also contributes to the NATO Combined Air Operations Center at the Torrejon air base outside Madrid, an allied command center that also will participate in the development of the anti-missile shield.

"Spain is a supportive and committed member of Europe's collective defense," the Socialist prime minister said, adding that he has kept the main opposition Popular Party informed of developments in this regard.

Plans to host the U.S. ships will be approved at an upcoming Cabinet meeting and, once all the details have been hammered out, Washington and Madrid will sign a definitive agreement, government spokespersons said.