During the Cold War nuclear weapons had the perverse effect of making the world a relatively stable place. That is no longer the case. Instead, the world is at the brink of a new and dangerous phase - one that combines widespread proliferation with extremism and geopolitical tension.

Some of the terrorist organisations of today would have little hesitation in using weapons of mass destruction to further their own nihilistic agendas. Al-Qaeda and groups linked to it may be trying to obtain nuclear material to cause carnage on an unimaginable scale. Rogue or unstable states may assist, either willingly or unwillingly; the more nuclear material in circulation, the greater the risk that it falls into the wrong hands. And while governments, no matter how distasteful, are usually capable of being deterred, groups such as al-Qaeda, are not. Cold War calculations have been replaced by asymmetrical warfare and suicide missions.

There is a powerful case for a dramatic reduction in the stockpile of nuclear weapons. A new historic initiative is needed but it will only succeed by working collectively and through multilateral institutions. Over the past year an influential project has developed in the United States, led by Henry Kissinger, George Shultz, William Perry and Sam Nunn, all leading policymakers. They have published two articles in The Wall Street Journal describing a vision of a world free of nuclear weapons and articulating some of the steps that, cumulatively taken, could help to achieve that end. Senator John McCain has endorsed that analysis recently. Barack Obama is likely to be as sympathetic.

A comparable debate is now needed in this country and across Europe. Britain and France, both nuclear powers, are well placed to join in renewed multilateral efforts to reduce the number of nuclear weapons in existence. The American initiative does not call for unilateral disarmament; neither do we. Instead, progress can be made only by working alongside other nations towards a shared goal, using commonly agreed procedures and strategies.

The world's stockpiles of nuclear weapons are overwhelmingly controlled by two nations: the United States and Russia. While Washington is in possession of about 5,000 deployed warheads, Russia is reported to have well over 6,000, making its stockpile the largest in the world. It is difficult to understand why either the American or Russian governments feel that they need such enormous numbers of nuclear weapons.

Hard-headed Americans, such as Dr Kissinger and Mr Shultz, have argued that dramatic reductions in the number of nuclear weapons in these arsenals could be made without risking America's security. It is indisputable that if serious progress is to be made it must begin with these two countries.

The US and Russia should ensure that the Strategic Arms Reduction Treaty of 1991 continues to provide the basis for co-operation in reducing the number of nuclear weapons. The treaty's provisions need to be extended. Agreement should be reached on the issue of missile defence. The US proposal to make Poland and the Czech Republic part of their missile defence shield has upset the Kremlin. It has been a divisive issue, but it need not be. Any missile threat to Europe or the United States would also be a threat to Russia. Furthermore, Russia and the West share a strong common interest in preventing proliferation.

Elsewhere, there are numerous stockpiles that lie unaccounted for. In the former Soviet Union alone, some claim that there is enough uranium and plutonium to make a further 40,000 weapons. There have been reports of nuclear smuggling in the Caucasus and some parts of Eastern Europe. Security Council Resolution 1540, which obliges nations to improve the security of stockpiles, allows for the formation of teams of specialists to be deployed in those countries that do not possess the necessary infrastructure or experience in dealing with stockpiles. These specialists should be deployed to assist both in the monitoring and accounting for of nuclear material and in the setting up of domestic controls to prevent security breaches. Transparency in these matters is vital and Britain can, and should, play a role in providing experts who can fulfil this important role.

The Non-Proliferation Treaty, for 40 years the foundation of counter- proliferation efforts, in in need of an overhaul. The provisions on monitoring compliance need to be strengthened. The monitoring provisions of the International Atomic Energy Agency's Additional Protocol, which require a state to provide access to any location where nuclear material may be present, should be accepted by all the nations that have signed up to the NPT. These requirements, if implemented, would have the effect of strengthening the ability of the IAEA to provide assurances about both declared nuclear material and undeclared activities. At a time when a number of countries, including Iran and Syria, may be developing a nuclear weapons programme under the guise of civilian purposes, the ability to be clear about all aspects of any programme is crucial.

Bringing the Comprehensive Test Ban Treaty into effect would, similarly, represent strong progress in the battle to reduce the nuclear threat. The treaty would ban the testing of nuclear weapons, ensuring that the development of new generations of weapons ceases. However, it will only come into force once the remaining nine states who have not yet ratified it do so. Britain, working through Nato and the EU, must continue to encourage those remaining states that have not yet agreed to the Treaty - India, Pakistan, Egypt, China, Indonesia, North Korea, Israel, Iran and the United States - to ratify it.

A modern non-proliferation regime will require mechanisms to provide those nations wishing to develop a civilian nuclear capability with the assistance and co-operation of those states that possess advanced expertise and that are able to provide nuclear fuel, spent-fuel management assistance, enriched uranium and technical assistance. But, in return, proper verification procedures must be in place and access for the IAEA must not be impeded.

Achieving real progress in reducing the nuclear weapons threat will impose obligations on all nuclear powers not just the US and Russia. The UK has reduced its nuclear weapons capability significantly over the past 20 years. It disposed of its freefall and tactical nuclear weapons and has achieved a big reduction of the number of warheads used by the Trident system to the minimum believed to be compatible with the retention of a nuclear deterrent. If we are able to enter into a period of significant multilateral disarmament Britain, along with France and other existing nuclear powers, will need to consider what further contribution it might be able to make to help to achieve the common objective.

Substantial progress towards a dramatic reduction in the world's nuclear weapons is possible. The ultimate aspiration should be to have a world free of nuclear weapons. It will take time, but with political will and improvements in monitoring, the goal is achievable. We must act before it is too late, and we can begin by supporting the campaign in America for a non-nuclear weapons world.

Sir Malcolm Rifkind, Lord Hurd of Westwell and Lord Owen are all former foreign secretaries; Lord Robertson of Port Ellen is a former Nato secretary-general

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