The growing number and modernization of ballistic missiles in the Asia-Pacific region poses a security challenge for the United States and its allies and is thus a concern for many in Congress. The United States has made ballistic missile defense (BMD) a central component of protection for forward-deployed U.S. forces and extended deterrence for allied security. The configuration of sensors, command-and-control centers, and BMD assets in the region has slowly evolved with contributions from treaty allies, primarily Japan, Australia, and South Korea.
Observers believe that North Korea has an arsenal of hundreds of short-range ballistic missiles and likely dozens of medium-range Nodong missiles; the extended-range Nodongs are considered capable of reaching Japan and U.S. bases there. Longer-range North Korean missiles appear to be under development but remain unreliable, with only one successful test out of five in the past 15 years. The U.S. intelligence community has not yet concluded that North Korea can build nuclear warheads small enough to put on ballistic missiles, but there is significant debate among experts on this question.
Full Report: Ballistic Missile Defense in the Asia-Pacific Region: Cooperation and Opposition (PDF)
Source: Congressional Research Service (via Federation of American Scientists)