Secret Defense Department studies cast doubt on whether a multibillion-dollar missile defense system planned for Europe will ever be able to protect the U.S. from Iranian missiles as intended, congressional investigators say.

Military officials say they believe the problems can be overcome and are moving forward with plans. But proposed fixes could be difficult. One possibility has already been ruled out as technically unfeasible. Another, relocating missile interceptors planned for Poland and possibly Romania to ships on the North Sea, could be diplomatically explosive…

The officials who spoke to the AP emphasized that the interceptor intended to protect the United States is in the early stages of development and its capabilities are not known. They said that the U.S. is already protected by other missile defense systems. Even if European-based interceptors are unable to directly defend the United States, they say they would protect not only European allies and U.S. troops stationed on the continent, but also U.S. radars there that are necessary for all U.S. missile defense plans.