Iran will meet representatives from the EU and six world powers next week for talks about its nuclear programme. The hope must be that an accord can be reached allaying fears that Tehran is seeking to build a nuclear bomb. This remains the world’s major security threat – and one that could yet see Iran, Israel and the US descend into a new regional conflict.

Confronting the challenge posed by Iran and North Korea is not the only issue facing the US and its allies as they deal with potential nuclear proliferation. They must also occupy more of the moral high ground that allows them to argue that other countries should not enter the nuclear weapons club. One of President Obama’s outstanding foreign policy achievements in his first term has been to push the US and Russia – which between them have 95 per cent of the world’s nukes – to cut the number of nuclear weapons they have. He has also declared abolition of these weapons to be a long-term policy goal for the US.

If Mr Obama wins a second term, he should push ahead with further cuts. Today, Global Zero, an international movement endorsed by the US president, spells out in detail what the next step should be. In a paper, General James Cartwright, the former commander of US Strategic Command, argues that the US and Russia should cut their nuclear weapons from the current level of 5,000 on each side (in active deployed and reserve arsenals) to about 900 within the next 10 years.