Major world powers have begun two days of talks with Iran over its controversial nuclear programme. Diplomats meeting in Istanbul, Turkey are expected to revive a fuel-swap plan, where Iran gives up nuclear material in return for fuel for a research reactor. The talks are being chaired by European Union foreign policy chief Baroness Ashton. The Iranian delegation is led by the country’s top nuclear negotiator, Saeed Jalili. Negotiators from China, France, Germany, Russia, the UK and US are meeting Iranian officials. The US diplomats, however, warned that major breakthroughs were unlikely. The West suspects Iran aims to build nuclear weapons, and has imposed economic sanctions. Tehran insists its nuclear programme is peaceful.