At a time when the US attention is focused on securing Pakistan's nuclear arsenal, India has taken a giant step towards creating a missile shield that can shoot down incoming nuclear-tipped rockets while they are too far away to do serious damage.

India's Defence R&D Organisation has announced that it would conduct a full-scale test of a two-stage anti-ballistic missile system by June 2008.

If the test is as successful as the last two tests on November 27, 2006, and December 7, 2007, vulnerable Indian cities like New Delhi will soon be protected by missile units, putting a serious question mark over Pakistan's ability to strike the Indian capital.

It was this Pakistani threat during the Kargil conflict in 1999, and again when Indian forces were deployed for war after the attack on Parliament in December 2001, that held back India from full-scale war.

The DRDO announcement follows a successful test last Friday off the Orissa coast, in which a DRDO interceptor missile shot down a simulated enemy missile. The "enemy" missile was actually an Indian Prithvi missile that was fired by the army.

On Wednesday, VK Saraswat, the DRDO's Chief Controller of Missiles and Strategic Systems, showed media persons a video recording of the missile test. While the "enemy" missile was still 15 km above the ground, and barrelling towards its target at a speed of 2 km per second, the DRDO interceptor missile smacked into it, breaking it into debris.

In the first test in November last year, the interceptor missile had brought down the "enemy" missile while it was 78 km above the ground.

The DRDO says that the complete ABM system, which will eventually protect important Indian targets, will combine both systems: one set of interceptors will be fired to bring down the incoming rocket at altitudes of about 80 km. If it survives, another set will target it at altitudes of about 15 km. The former is termed an 'exo-atmospheric interceptor' and the latter an 'endo-atmospheric' one. The former has been christened 'Pradyumna' by the DRDO. The latter will soon get a name.

Saraswat pointed out that India's nuclear doctrine stipulates "no first use" of nuclear weapons. That gives any enemy the first chance to target India with nuclear strikes. India, he said, must therefore, have the means to protect itself against that first wave of nuclear attacks.

The DRDO's high- profile Guided Missile Development Programme, which set former president APJ Abdul Kalam [Images] on the path to fame, has had a patchy record.

While the Prithvi and the Agni ballistic missiles can arguably be termed successes, the medium range Akash and Trishul missiles have not yet proved successful. The new ABM system was not originally a part of the GMDP.

When asked how the ABM system had overcome the problems that continue to plague the Akash and Trishul programmes, Saraswat told Business Standard that the new ABM missiles had homing heads that sensed the targets and took the interceptor missiles towards it.

They did not use the Akash and Trishul missiles' technically problematic 'command guidance' method, in which radio signals are sent from a ground station to guide the missile towards the target.

ABM systems are controversial; strategists argue that they destabilise nuclear deterrence by giving one country the ability to ward off nuclear strikes, thus encouraging it to attack.

Cold War adversaries, America and the Soviet Union, signed an ABM Treaty in 1972, undertaking not to develop ABM systems. Saraswat, however, defended India's coming ABM shield, saying, "our ABM system is a defensive posture, not an offensive posture."