Earlier in the day the United States reached an agreement with Romania to establish an interceptor facility at a former air base in the south of the Balkan country for a future defense shield, the first such deployment in Europe.

Russia is keeping a sharp eye on the deployment of elements of the U.S. missile defense system in Romania, the Russian Foreign Ministry said.

"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," the statement said.

"This issue should be resolved swiftly. 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," the statement said.

"We regretfully say that practical steps to create the European segment of the global missile defense shield of the United States are being taken with no regard to Russian-U.S. dialogue on the anti-missile issue started under the initiative of presidents Dmitry Medvedev and Barack Obama, as well as to the work under the Russia-NATO Council's Lisbon Summit aimed to draft a European missile defense system," the Russian document said.