BRUSSELS (Reuters) - The United States and Spain have reached an agreement that will strengthen efforts to build a missile defense system in Europe by basing U.S. anti-missile warships at the Rota navy base on Spain's southwestern coast, senior U.S. defense officials said.
The agreement was to be formally announced later on Wednesday at NATO headquarters in Brussels by Spanish President Jose Luis Rodriguez Zapatero, NATO Secretary General Anders Fogh Rasmussen and U.S. Defense Secretary Leon Panetta.
The basing agreement is part of President Barack Obama's so-called phased adaptive approach to missile defense, which calls for an initial deployment of ship-based anti-ballistic missiles in the eastern Mediterranean followed by ground-based systems in Romania and Poland.
Senior U.S. defense officials said the basing agreement was extremely efficient for the United States.
The basing agreement at Rota, on the Atlantic coast near Cadiz, "strengthens our continuing presence in the Mediterranean" and will "contribute to security in the Med as well as in the eastern Atlantic," a defense official said.
"You probably need 10 of these ships if they were based in the eastern U.S. to be able to ... transit across the ocean back and forth to patrol in the Med," he said. "By having the ability to home port them in ... Rota, we're able to maintain this continuous presence at lower costs, four ships instead of 10."
The United States is committed to having at least one ship on station at all times in the eastern Mediterranean, where their anti-missile missiles would be most effective, the defense official said. Having them based in Rota would enable more than one to be in the eastern Mediterranean as needed.
"The key ... is it's going to give more weight to the European Phased Adaptive Approach," the defense official said, noting that it follows the recent agreement to base U.S. early-warning radar in Turkey.
The ships also would be part of the pool of vessels available to participate in standing NATO maritime groups, which are used for counterpiracy and other missions, he said.
The Obama administration launched the phased adaptive approach to missile defense in 2009 and abandoned former President George W. Bush's plan to build a land-based missile defense system in Poland and the Czech Republic.
The decision helped to reduce friction with Russia, which had expressed concerns the system was targeting its nuclear deterrent. The Bush administration said the system was aimed at what he called "rogue" states like Iran and North Korea which are developing longer-range missiles and have nuclear programs.
(Reporting by David Alexander; Editing by Mark Heinrich)