US Defence Secretary Chuck Hagel has scrapped the final phase of its European missile defence shield, citing development problems and funding cuts.
Upgraded interceptors were to have been deployed in Poland to counter medium- and intermediate-range missiles, and potential threats from the Middle East.
Mr Hagel said the threat had "matured" and that the US commitment to Nato missile defence remained "ironclad".
"Rightful liberty is unobstructed action according to our will within limits drawn around us by the equal rights of others. I do not add 'within the limits of the law' because law is often but the tyrant's will, and always so when it violates the rights of the individual." Thomas Jefferson