Technology issues: Will the United States be able to develop and deploymissile defenses that can intercept missiles of all ranges and at all phases of their flights? The report concludes with a summary of congressionalaction on the missile defense budget. Missile Defense Prior to the Bush Administration

The United States has pursued the development of missile defenses for more than 50 years. Missile defense has provento be a challenging and elusive endeavor. Moreover, the question of whether the United Statesshould deploy extensive defenses to protect against ballistic missile attack has been one of the mostdivisive political and national security issues of this generation. For many, concerns about nuclear stabilitybetween the United States and Russia have receded as the two nations expanded their areas ofcooperation and improved their relationship, especially in the U.S. lead war on terrorism. (1) Eventerrorist acquisition of ballistic missiles armed with weapons of mass destruction is today part of thepolicy debate. Bush Administration's Proposed Approach

The Bush Administration sharply altered the debate over missile defense. In its missile defense program, the Bush Administration eliminated distinctions betweentheater and national missile defenses (TMD and NMD). Unlike theClinton Administration, the Bush Administration has not yet identified an architecture (a detailedmissile defense system with specific objectives and capabilities) that it will seek to deploy norestablished a schedule for the development and deployment of any particular system or element; but,a clear underlying objective is the early deployment of a defense designed against missiles aimed atU.S. territory. Actual withdrawal from the 1972 ABM Treaty occurredJune 13, 2002. Russia has the most significant ballisticmissile inventory of all countries of concern. (12) 
China. Previously, the United Statespursued missile defense concepts that employed nuclear weapons as interceptors. Layered Defenses. Acquisition Strategy & Congressional Oversight. (39)
The Administration and its supporters argue that the use of spiral development for the missiledefense program (or other weapon acquisition programs) will not prevent Congress from conductingeffective oversight, and could even improve Congress's oversight ability in some respects, becauseCongress will retain its role in approving each block, or segment, in a spiral development program,and because the information that DOD provides for the block to be approved will be more reliablethan the potentially speculative information it might present under the traditional acquisitionapproach about what the entire program might look like from beginning to end. TheAdministration said the United States would begin fielding initial missile defense capabilities in2004-2005 to meet the near-term ballistic missile threats to the U.S. homeland, to U.S. deployedforces, and to counter ballistic missile threats to U.S. friends and allies. New Missile.
The United States has pursued missile defenses since the dawn of the missile age shortly afterWorld War II. The development and deployment of missile defenses has not only been elusive, buthas been one of the most divisive issues of the past generation until recent years.
The Bush Administration substantially altered the debate over missile defenses. TheAdministration requested significant funding increases for missile defense programs, eliminated thedistinction between national and theater missile defense, restructured the missile defense programto focus more directly on developing deployment options for a "layered" capability to interceptmissiles aimed at U.S. territory across the whole spectrum of their flight path, adopted a new, untrieddevelopment and acquisition strategy, announced U.S. withdrawal from the 1972 Anti-ballisticMissile Treaty, and has deployed an initial national missile defense capability.
The Administration argued these steps were necessary in response to growing concerns overthe spread of weapons of mass destruction and their means of delivery, especially on the part of ahandful of potentially hostile states and terrorists. In addition, they asserted that U.S. deterrencetheory has outlived its usefulness and that conventional or nuclear deterrence could not be reliedupon to dissuade unstable leaders in rogue states.
Critics, however, take issue with assertions that the threat is increasing, citing evidence thatthe number of nations seeking or possessing nuclear weapons has actually declined over the past 20years. Moreover, they argue that the technology for effective missile defense remains immature, thatdeployment can be provocative to allies, friends, and adversaries, and it is a budget-buster thatreduces the availability of funds to modernize and operate U.S. conventional military forces. Theyargue especially that some major powers view U.S. missile defense as an attempt at strategicdomination and that other, such as China, will expand their missile capabilities in response.
This report will be updated as needed.