As President Clinton ponders deployment of a proposed National Missile Defense (NMD) system, skyrocketing costs and significant technical problems mean the U.S. has no effective or affordable missile defense at this time.

The Pentagon recently estimated the overall price tag of building and operating a national missile defense system from 1991 to 2026 at more than $30 billion. That is 138% more than the $12.7 billion cost estimate frequently cited by the Clinton Administration.

Similarly, the non-partisan U.S. Congressional Budget Office estimated that costs have increased by $5 billion over the $12.7 billion figure.

These new cost figures come at a critical time for the program. President Clinton is only a few months away from deciding whether or not to deploy the system. Military planners say he must decide by this fall in order to complete NMD site preparation and meet a 2005 deployment date.

The rising cost estimate may be the crucial factor in the decision because President Clinton has identified cost as one of the four criteria on which he will base his decision whether or not to deploy NMD.

About three-quarters of the cost increase stems from the growing scope of the missile defense system envisioned by the Pentagon. Also, a portion of the higher cost stems from emerging technical problems and changing demands. These cost factors include radar and computer upgrades, and more expensive flight tests even as fewer such tests are planned.

These numbers come as military and defense contractors scramble to produce a second successful test for the controversial system. In the most recent flight test in January, the interceptor missed its dummy warhead target in space over the Pacific Ocean when the cooling system malfunctioned.

Critics have also questioned the scope and effectiveness of NMD technology. NMD would not be able to cope with a massive nuclear attack of the kind Russia or China could launch, but would instead be designed to shoot down a few incoming missiles launched by potential enemies such as North Korea, Iran or Iraq.

But a recent study by the Union of Concerned Scientists and top MIT defense experts concluded that potential enemies could easily render NMD useless by employing simple, cheap countermeasures to confuse and outnumber radar and interceptors.

Until the full facts about overall taxpayer costs are known and technical problems of the program are fixed, President Clinton should delay his decision on deployment. Asking taxpayers to invest billions in an NMD system that currently doesn't provide adequate protection may prove to be a costly and avoidable mistake.