The U.N. panel on climate change warns of mass extinctions, droughts, floods and fires. Less remarked upon but also disturbing: The effort to slow global warming could speed up the spread of nuclear weapons. We need a new approach to avoid global warming and nuclear proliferation merging into an environmental and security nightmare.

Why? Global electricity demand is growing quickly. Meeting that demand with coal-fired plants will continue to spill massive amounts of greenhouse gases into the atmosphere. The only hope to confront global warming effectively is to do all we can to conserve energy, expand renewable sources - and, yes, build more nuclear power plants.

Demand is growing so fast that the world will need to build about 1,000 reactors by 2050 to maintain nuclear's current 16 percent share of global electricity supplies. Thirty reactors are under construction in 12 countries, with many more planned or ordered.

More reactors, however, means more enriched uranium and more plutonium-laced spent fuel. If the facilities to handle these materials also proliferate, more and more countries will end up with the bomb capability we have tried so hard to keep out of Iranian and North Korean hands. Anxious neighbors may then decide that they, too, need to develop their own bomb capabilities - if not the bomb itself - as a matter of pride or security.

The spread of nuclear weapon capabilities could spark instability, strip support for nuclear energy or, worst of all, lead to the actual use of nuclear weapons. In addition to the human toll and the blow to global peace and stability, nuclear proliferation could ruin the possibility that nuclear energy can help in the fight against global warming.

How can we preserve the ability of nuclear energy to reduce global warming without sparking a nuclear arms race? Fortunately, uranium enrichment and plutonium separation technologies are complex and expensive. So nations that seek nuclear energy but not weapons may opt to buy or lease nuclear fuel rather than building their own plants, just as most have opted to buy or lease (rather than build) their own commercial airliners.

In that spirit, the suppliers of nuclear fuel services should offer cradle-to-grave fuel services on attractive commercial terms to nations building nuclear reactors. Before they give up their own option to build enrichment and reprocessing plants, governments would need solid guarantees that their services would only be interrupted in response to a material breach of their nonproliferation obligations.

In order to be credible, these guarantees could be backed by the International Atomic Energy Agency, which can serve as the supplier of last resort as well as the appropriate authority to judge whether a material breach has occurred. Of course, discovery of a clandestine bomb program outside of a country's safeguarded nuclear facilities would dissolve the fuel guarantee and open the door to action against the offending state by the U.N. Security Council.

This approach would greatly reduce the incentives for countries purely interested in energy to build those troublesome facilities, while inviting appropriate international scrutiny upon those nations (like Iran and North Korea) that insist on developing technologies perfectly suited to bomb production, though they lack a credible energy or economic justification.

Existing nuclear fuel suppliers - nations and companies - should quickly agree to such an approach, before so many other nations have embarked on their own nuclear fuel programs that it is too late to turn back. To maintain a level playing field - and pressure on the negotiators - the U.N. Security Council should call for a moratorium on building new enrichment and reprocessing plants while the terms of this new regime are being negotiated.

It will be painful for governments to give up their ability to cut off nuclear fuel services on political grounds, such as human rights abuses or other valid concerns about another government's conduct. But the stakes for nuclear proliferation are too high to be held hostage to other considerations, even important ones. Even worse would be failure to act now, before our efforts to fight nuclear proliferation and climate change end up accelerating one or both.

Daniel Poneman, who served on the National Security Council staff under Presidents George H.W. Bush and Bill Clinton, is a principal in an international advisory firm working in areas including the nuclear industry.