Moscow is preparing to welcome the US President to Russia on his first visit, but the two sides still are still struggling to reach agreement on how to cut their Cold War arsenals of nuclear weapons.There is little doubt that the summit comes at a time of renewed harmony between the two superpowers, after relations hit a low under Obama’s predecessor not seen since the Cold War. But nonetheless the pair still have major hurdles to overcome if they are to find a replacement for the 1991 Strategic Arms Reduction Treaty – or START – that expires in December. Russia’s President Medvedev has said America must compromise on its planned missile shield in eastern Europe if a new START deal is to materialise. America says it is to guard against what it calls ‘rogue states’ particularly Iran. But Moscow feels threatened. Obama told a Russian newspaper that the US has not yet decided its missile defence configuration in Europe, and added that he hoped Russia will be a partner in that project. The framework on Strategic nuclear weapons was supposed to be the centrepiece of the Moscow summit. But negotiators have their work cut out to have a document ready in time.