Last week the US, Europe, Russia and China jointly condemned Iran’s refusal to explain how it got blueprints and equipment usable for making nuclear bomb fuel. Tehran has been defying the spirit of the Nuclear Nonproliferation Treaty in order to acquire the technology and fuel. If it is allowed to continue, it could begin building bombs in two to five years. It has been concealing suspicious nuclear activities from the International Atomic Energy Agency since at least 1985. In recent days, Tehran has threatened to resume work on uranium-enrichment equipment. Europe should overcome its qualms about referring the Iranian nuclear issue to the UN Security Council. The Council is designed to deal with threats to international peace and security. A potential Iranian breakout from the NPT clearly qualifies. Russia should continue to refrain from delivering fuel for Iran’s Russian-built nuclear power reactor until Tehran renounces uranium enrichment and cooperates with the IAEA. China should order its companies not to cooperate with Iranian enrichment and should urge North Korea and Pakistan to impose such bans. The unhappy experience of Iraq showed that unilateral military action is not a very useful antiproliferation tool. This is the moment to make multilateralism, pursued with determination and firmness, work with Iran. — The New York Times