Steven Weinberg

About the author: Steven Weinberg, a Nobel Prize winner in physics, has been a consultant to government agencies on national defense issues. His writings include The First Three Minutes and Dreams of a Final Theory.

America does not face a fixed missile threat. Attempting to construct a national missile defense system that would take years to fully deploy may provoke other nations into increasing their nuclear arsenals, making America less secure. Pursuing missile defense may also weaken America's national security by taking away funds from other defense and security programs, such as programs to prevent nuclear proliferation. The employment of a missile defense system would also harm American relations with other countries.

Would a national missile defense system of the sort proposed by the...