GENEVA (Reuters) - Negotiations between Iran and six world powers will resume on Saturday morning after top diplomats from the United States, Iran and European Union made progress during talks on Tehran's nuclear program, a senior U.S. State Department official said. "Over the course of the evening, we continued to make progress as we worked to narrow the gaps," the official said late on Friday after Secretary of State John Kerry, Iranian Foreign Minister Mohammad Javad Zarif and EU foreign policy chief Catherine Ashton met for five hours. ...