South Africa disowned and dismantled its nuclear weapons after the collapse of the apartheid regime. New states to emerge from the Soviet Union, such as Ukraine, renounced the nuclear systems they inherited on their territory. Argentina and Brazil dropped the nuclear capability they were developing after negotiating a non-nuclear pact between themselves. Even Iraq turned out to have abandoned its nuclear weapons programme, although in that particular case the success of the non-proliferation regime was more of an embarrassment to George Bush.

Previous review conferences, which come round every five years, have been used as an important opportunity to regenerate support for the treaty. Not this time. The full weight of Washington diplomacy was focused on preventing any reference in the agenda to the commitments the Clinton administration gave to the last review conference. As a result, the first two weeks of negotiation were taken up with arguing over the agenda, leaving barely one week for substantive talks. Robert McNamara, the former US defence secretary and no peacenik, has observed that if the people of the world knew "they would not tolerate what's going on in the NPT conference".

Observance of the non-proliferation treaty rested on a bargain between those states without nuclear weapons, who agreed to renounce any ambition to acquire them, and the nuclear-weapon powers, who undertook in return to proceed in good faith to disarmament. It suits the Bush administration now to present the purpose of the treaty as halting proliferation, but its original intention was the much broader ambition of a nuclear-weapon-free world. The acrimonious exchanges inside the present review conference reflect the frustration of the vast majority of states, who believe they have kept their side of the deal by not developing nuclear weapons but have seen no sign that the privileged elite with nuclear weapons have any intention of giving them up.

It was to bridge the growing gulf between the two sides that the British delegation, led by Peter Hain, at the last review conference in 2000 helped broker agreement to 13 specific steps that the nuclear-weapon powers could take towards disarming themselves. Labour scores reasonably well against those benchmarks. Britain has taken out of service all non-strategic nuclear weapons and as a result has disarmed 70% of its total nuclear explosive power. It has also halted production of weapons-grade material and placed all fissile material not actually in warheads under international safeguards. This positive progress will be comprehensively reversed if Tony Blair does proceed as threatened to authorise construction of a new weapons system to replace Trident, but until then Britain has a good story to tell.

Not that it gets heard in the negotiating chambers, where it is obscured by our close identification with the Bush administration and our willingness in the review conference to lobby for understanding of their position. Their position is simply stated: obligations under the non-proliferation treaty are mandatory on other nations and voluntary on the US. Even while the review conference was sitting, the White House asked Congress for funds to research a bunker-busting nuclear bomb, although to develop new nuclear weapons, especially ones designed not to deter but to wage war, is to travel in the opposite direction to the undertakings the US gave to the last review conference.

The rationale for the bunker-buster is revealing. Its objective is to penetrate and destroy deeply buried arsenals of weapons of mass destruction. Perversely, the current regime in Washington does not perceive its development of nuclear weapons as an obstacle to multilateral agreement on proliferation but as the unilateral means of stopping proliferation. Whatever may be said for this muscular approach to proliferation, there is for sure no prospect of negotiating an agreed text with the rest of the world legitimating it.

Any progress within the non-proliferation treaty is therefore likely to be on hold until George Bush is replaced by a president willing to return to multilateral diplomacy. This is worrying as there are other pressing problems that should not be left waiting.

One of the design flaws of the treaty dates from its negotiation in the pre-Chernobyl era of rosy optimism about nuclear energy. As a result it turned on a deal in which the nuclear powers undertook to transfer peaceful nuclear know-how in return for other nations forswearing the military applications of nuclear technology. At the time many of us warned that it was inconsistent to enshrine the spread of nuclear energy in a treaty trying to halt the spread of nuclear weapons.

It therefore is no surprise that we now have a crisis over the advanced nuclear ambitions of Iran. One of the weaknesses in the west's negotiating position is that there is nothing in the non-proliferation treaty to prohibit Iran from acquiring a declared nuclear energy programme, although it seems implausible that the country has any urgent need for one, as it practically floats on a lake of oil.

The desirable solution is for an addition to the treaty banning countries without nuclear weapons from developing a closed fuel cycle for nuclear energy, which would stop them acquiring the fissile material for bombs. But this would deepen the present asymmetry between the nuclear powers and everyone else, and is only going to be negotiable if there is some evidence that we are serious about disarmament.

If the review conference breaks up in failure to agree, I suspect there will be some in Washington celebrating tonight, perhaps not in anything as foreign as French champagne but in the Napa Valley imitation. Within their own narrow terms they will have succeeded. They will have stopped another multilateral agreement and will have escaped criticism for not fulfilling their commitments under the last one. But in the process they will have weakened the non-proliferation regime and made the world a more dangerous place. The next time they lecture us on their worries about weapons of mass destruction, they do not deserve to be taken seriously.