US President Barack Obama has said the world must unite to stop the spread of nuclear weapons.At a specially convened summit, the UN Security Council unanimously approved a resolution put forward by Obama calling on states to scrap their atomic arsenals. Obama also warned the next few months would be critical in the fight against proliferation. “The world must stand together, we must demonstrate that international law is not an empty promise, and the treaties will be enforced. The next 12 months will be absolutely critical in determining whether this resolution and our overall efforts to stop the spread and use of nuclear weapons are successful,” Obama said. It is the first time a US president has chaired such an event and only the fifth time the Security Council has met with heads of state and government. The Russian President Dmitri Medvedev said: “Russia and the United States have already made unprecedented cuts in their strategic nuclear arsenals. Moreover, we have said many times and I confirm it now, we are ready to move further and to cut the number of carriers of strategic nuclear weapons by up to three times more, this proposal is now on the table for bilateral talks with our American partners.” Iran and North Korea were not named in the US draft but both countries’ nuclear ambitions are of deep concern to the world’s official atomic powers. Only yesterday, Russia hinted it might be ready to get tougher with Iran over its weapons programme.