Russia's chief negotiator was cautiously upbeat Friday about nuclear talks between Iran and six world powers, saying the number of issues still to be resolved before a June 30 deadline "can be counted on one hand". "Some complex issues remain but there are fewer of them than a week ago," Russian news agency RIA-**vosti quoted negotiator Sergei Ryabkov as saying at the latest round of talks in Vienna. Iran and the P5+1 powers -- the United States, Russia, China, Britain, France and Germany -- agreed in April on the main outlines of what would be a historic agreement scaling down Tehran's nuclear programme.