his year marks the 40th anniversary of the Nuclear Non-Proliferation Treaty's coming into force. Despite its central role in shaping the global nuclear order, the NPT's future looks anything but promising.

The main challenges the NPT now faces come from within its regime, not from the non-parties. The nations outside the NPT fold that wanted to go nuclear have done so. And having acquired nuclear weapons, those states are in no position to join a treaty that essentially is rigidly structured and is thus not amendable.

It has been widely forgotten that the NPT originally was intended to prevent countries like Japan, West Germany and Italy from acquiring nuclear weapons. Japan, did not ratify the treaty until 1976 — eight years after the NPT was concluded, and six years after the pact took effect. West Germany and Italy deposited their instruments of ratification only in 1975.

After France conducted its first nuclear test in 1960 in the Sahara, West Germany was considered the most likely candidate to follow suit. West Germany first tried to block the conclusion of the NPT before seeking to influence the outcome of the negotiations.

Over the years, however, the challenges to the NPT have come from outside the list of its original targets. NPT's first test, in fact, came early — in May 1974 when India carried out a "peaceful nuclear explosion" (PNE). As India was a non-signatory and indeed had vowed to stay out of the NPT when the treaty was concluded, the test involved no breach of legal obligations. Still, after the Indian test, PNEs quickly fell out of international favour, although the US and the Soviet Union both had large PNE programmes.

It is remarkable that the NPT has survived for so long and that it actually was extended indefinitely in 1995. As a result of the 1995 action, the treaty — originally conceived as a 25-year bargain between nuclear-weapons states and non-nuclear-weapons states — has become permanent. It is that success that has bred major challenges. Since the mid-1990s, the integrity and credibility of the NPT have come under growing pressure.

In fact, nearly a century after chemical arms were introduced in World War I and more than six decades following the nuclear incineration of Hiroshima and Nagasaki, the world is at the threshold of new lethal weapons, as underlined by the ongoing research on lasers, information weapons, space-based platforms, anti-satellite weapons and directed energy systems. For the foreseeable future, however, nuclear weapons, with their unparalleled destructive capacity, are likely to remain at the centre of international power and force. Nuclear weapons, as the 2002 US nuclear posture review stated, will continue to play a "critical role" because they possess "unique properties".

Yet, such are the challenges from the accelerated weaponisation of science that rearmament today looms large on the horizon, with the arms race being extended to even outer space. For example, the reverberations from China's January 2007 anti-satellite (ASAT) weapon test — the first ASAT kill by any power in more than two decades — continues to be felt because of the way that test brought down wishful thinking about averting militarisation of space.

ome 95% of all nuclear weapons are in the arsenals of the United States and Russia. The United States has officially announced recently that it has 5,113 nuclear weapons in its arsenal, plus "several thousand" more waiting to be dismantled — figures that match the estimates that were known publicly. Russia is believed to have fairly similar number of nuclear weapons in deployment, although the number of weapons in reserve could be more than in the United States. Although their arsenals have declined, both Russia and the US still maintain "overkill" capabilities — that is, either can destroy the entire world several times over. There can be no justification for maintaining such large arsenals.

The reductions proposed by the new Strategic Arms Reduction Treaty (START) between the US and Russia will not change the "overkill" capacities of the two sides. Under the treaty's terms, the United States and Russia would reduce their deployed warheads to 1,550 respectively.

The latest US Nuclear Posture Review (NPR), released recently, incorporates a welcome shift by proclaiming that the US will not use nuclear weapons against a non-nuclear-weapons state or in response to a non-nuclear attack. Yet that assurance is hedged with caveats — the non-nuclear-weapons states have to be "in compliance" fully with their non-proliferation obligations; and given the catastrophic potential of biological weapons, the US reserves the right to respond with nukes against a biological attack.

It would have been better had the posture review made clear — unequivocally and without any qualification — that the sole purpose of nuclear weapons is to deter a nuclear attack. Instead, the NPR declares such a sole purpose as a long-term goal. With the Nobel Peace Prize weighing heavily on Obama's mind, the caveat-ridden NPR comes across as being more posture than review.

Given the fact that every nuclear-weapons state, by definition, is a proliferator, the varying standards still being applied on proliferation underscore the non-proliferation challenges. Geopolitical interests, rather than objective criteria, usually determine a response to any proliferation problem. Also, who is a legitimate nuclear-weapons state or who is not has remained a subject of controversy. The NPT recognises as nuclear powers only those countries that tested a nuclear device before 1967. But it is hardly a good advertisement for the NPT regime that some nuclear-weapons states remain outside its fold.

Actually, the real "success" of the NPT has been in reinforcing the system of extended deterrence by giving countries such as those in NATO and others like Australia, Japan and South Korea little choice other than to continue to rely on the US for nuclear-umbrella protection. Minus the NPT, these countries would have been the most-likely candidates to go nuclear because they also happen to be the most-capable states technologically. So, the effect of the NPT has been to either strengthen extended deterrence or to drive nuclear programmes underground, as was symbolised by North Korea.

Today, the world has a treaty (although not in force) that bans all nuclear testing but no treaty to outlaw the use of nuclear weapons. In other words, those that are party to the Comprehensive Test Ban Treaty (CTBT) are prohibited from testing a nuclear weapon at home but are legally unencumbered to test the weapon by dropping it over some other state. That anomaly must be removed.