Post 1991 Gulf War, theatre missile defence (TMD) and national missile defence (NMD) have become two of the most keenly debated issues. These concepts were initially conceived to protect the continental United States, by providing early warning of incoming missiles and launching an interceptor missile ('kill vehicle') to collide with and destroy the approaching missile before it reached the target. However, the US is not achieving much technological success as hoped for by its security pundits.

A week back an important test of the United States missile defense system ended in failure as the interceptor rocket failed to launch on cue from the Marshall Islands. A rocket carrying a dummy warhead as the target was launched from Kodiak, Alaska. The interceptor missile, which was intended to go aloft 16 minutes later and home in on the target 100 miles over the earth failed to launch, reportedly because of an "an unknown anomaly".

The earlier test of the interceptor on 12 December 2002 was also a failure. The interceptor failed to separate from its booster rocket and missed its target by hundreds of miles and burnt up in the atmosphere. In 2003, a test of another part of the system, based on Navy ships, also failed. Before this last failure, the Missile Defense Agency had conducted eight tests with interceptor vehicles, scoring hits in five tests, but under carefully controlled conditions.

Presently, there are three distinct types of missile-defence capabilities at varying levels of technological maturity. First, 'lower-tier' systems designed for defence of specific sites or targets - more suitable for TMD; second, 'upper-tier' systems intended to intercept warheads in flight, and capable of covering a much wider area -more suitable for NMD, and, third, various types of sensors, radars and battle management capabilities intended to detect missile launches, thereby providing early warning of an imminent attack. Theoretically, a fourth level of capability is also possible, but is probably still at the stage of conceptualization. Here the aim could be to develop a system capable of intercepting and destroying missiles during their initial boost phase, that is, before the warheads or decoys break away from main system and head for their targets.

NMD technology is a classic case of politicizing a technology without even possessing it. This vital technology and security issue is being driven by people/countries having vested interests in viz. the armed services and the military industrial complex. The issue has also raised concerns amongst nation-states regarding the have and have-nots of the US NMD umbrella much before the availability of a actual working system.

It is reported that the overall missile defense program is expected to cost more than $50 billion over the next five years; the first group of land and sea-based missiles, sensors and associated systems envisioned for deployment would cost more than $7 billion, and the last test alone had a budget of $85 million. This requirement of huge investments in this project is expected to raise growing concerns in US political circles. The US has cut down NASA's budget drastically. Today, it is fighting a lonely 'urban warfare' in Iraq which has put tremendous pressure on the US economy. The Dollar is weakening vis-à-vis other currencies. Under these circumstances many within the US will challenge the continuance of these costly programmes.

Post 1991 Gulf war, the NMD programme was perceived as designed against WMD threats to the continental US and its allies from 'states of concern' like Iraq, Libya and North Korea. But, except for North Korea and Iran, the US is not threatened by any other 'states of concern' capable of launching a missile attack with a WMD warhead. Today, the WMD threat is more likely from non-state actors than state actors. Hence, it could be argued that the need for this system no longer exists.

Many experts simply do not think that an effective NMD shield can be developed in the foreseeable future. Currently the scientists are not even venturing to conceptualize the counter-measures against this system. It is predicted that the enemy could easily disrupt this system by paralyzing its electronic systems; or by using cruise missiles to flood the anti-ballistic missile shields; or simply overwhelm the defences by a saturation raid with large numbers of missiles.

However, it is not likely that the US will stop the development of this system. They will go ahead; quoting futuristic threats like China. US 'unilateralism' has reached a stage where it can drive the global strategic agenda even if it is based on unproven technologies.