A top Russian envoy is due in Iran for talks on Tehran's controversial nuclear programme, with the world community still unable to reach consensus on how to tackle the escalating crisis. Russian National Security Council chief Igor Ivanov is expected to hold talks with Iran's top nuclear negotiator Ali Larijani during his two-day visit. His trip follows a meeting this week of senior officials from Britain, France, China, Russia and the United States -- the five permanent UN Security Council members -- as well as Germany -- that failed to break an impasse on how to deal with Iran although progress was reported.