Just as nuclear energy seems poised for a global comeback, nuclear weapon threats grow in Iran and North Korea. The security risk from expanding nuclear energy programmes could potentially be contained by the commercial provision of nuclear-fuel services. Countries that already possess uranium enrichment and plutonium reprocessing facilities could guarantee client countries with cradle-to-grave nuclear fuel services. The guarantee, backed by governmental or international entities, could persuade governments to abstain from building their own fuel-cycle facilities. Decisions to reject such an arrangement, which provides direct economic benefit and relieves waste management challenges, would spotlight a government's intentions and invite a coordinated international response. Iran and Brazil present crucial early tests.