NEW DELHI - India has warned Pakistan that it will retaliate massively even if Pakistan used tactical nuclear weapons against it.

As Pakistan is developing "tactical" nuclear warheads to miniaturise its weapons to be carried on short-range missiles, India will protect its security interests by retaliating to a "smaller" tactical attack in exactly the same manner as it would respond to a "big" strategic attack.

Shyam Saran, convener of the National Security Advisory Board, said, "India will not be the first to use nuclear weapons, but if it is attacked with such weapons, its nuclear retaliation will be massive and designed to inflict unacceptable damage on its adversary. The label on a nuclear weapon used for attacking India, strategic or tactical, is irrelevant from the Indian perspective."

Saran was placing on record India's official nuclear posture with the full concurrence of the highest levels of nuclear policymakers in New Delhi.

Saran argued that as a result of its tactical weapons, Pakistan believes it has brought down the threshold of nuclear use.

"Pakistani motivation is to dissuade India from contemplating conventional punitive retaliation to sub-conventional but highly destructive and disruptive cross-border terrorist strikes such as the horrific 26/11 attack on Mumbai. What Pakistan is signalling to India and to the world is that India should not contemplate retaliation even if there is another Mumbai because Pakistan has lowered the threshold of nuclear use to the theatre level. This is nothing short of nuclear blackmail, no different from the irresponsible behaviour one witnesses in North Korea," he said.

One of the main reasons for Pakistan miniaturising its nukes is actually to keep its weapons from being confiscated or neutralised by the US, a fear that has grown in the Pakistani establishment in the wake of the operation against Osama bin Laden. "Pakistan has, nevertheless, projected its nuclear deterrent as solely targeted at India and its strategic doctrine mimics the binary nuclear equation between the US and the Soviet Union which prevailed during the Cold War," Saran said.

However, warning Pakistan, he added, "A limited nuclear war is a contradiction in terms. Any nuclear exchange, once initiated, would swiftly and inexorably escalate to the strategic level. Pakistan would be prudent not to assume otherwise as it sometimes appears to do, most recently by developing and perhaps deploying theatre nuclear weapons."

There have been significant shifts in Pakistan's nuclear posture recently. First is the movement from uranium to a newer generation of plutonium weapons, which has enabled Pakistan to increase the number of weapons, outstripping India in weapons and fissile material production. Although they are still to be verified, Pakistan has claimed it has miniaturised nuclear weapons to be used on cruise missiles and other short-range missiles. The newer generation of Pakistan's weapons are also solid-fuelled rather than liquid, making them easier to transport and launch, he said.