Officials said Tuesday the site selected was Deveselu Air Base, near Caracal in southern Romania, The New York Times reported.
The deployment of the SM-3 missiles for the missile defense system is expected by 2015, officials said. The base is part of a program designed to link the United States and NATO allies against an Iranian threat.
The announcement drew immediate complaints from Russia, which called for legal guarantees from the United States that the shield wouldn't target Russia's strategic nuclear forces, RIA Novosti reported.
"In this situation the necessity of legal guarantees from the United States that [its] missile defense system ... will not be aimed against Russia's strategic nuclear forces becomes even more crucial," a statement from the Russian Foreign Ministry said.
"This issue should be resolved swiftly," the statement said. "Moreover, we are sure that it is necessary ... to proceed to the coordination of the concept and the architecture of the European missile defense system as soon as possible."
U.S. officials dismissed the complaints, citing the United States and NATO asking Moscow to participate in a common missile-defense system for Europe.