Iran's top nuclear negotiator Ali Larijani on Tuesday deplored Russia's decision not ship nuclear fuel to Iran as agreed, a move that delays the start of Iran's first nuclear power plant. "This (Russian decision) shows that there is no such thing as a guarantee to deliver nuclear fuel," the official Islamic Republic News Agency quoted Larijani as saying Tuesday. Russia's federal nuclear agency, Rosatom, announced Monday that it would postpone the shipment of nuclear fuel to Iran because Iran had delayed payment for work on the Russian-built power plant outside this southern Iranian city. Iran rejected the Russian claim, saying it has fulfilled all its financial obligations. Rosatom spokesman Sergei Novikov told The Associated Press that the start of the reactor - scheduled for September - would be postponed by at least two months because the Iranians had made no payments since Jan. 17. "The funding is two months behind, and that means a corresponding delay in schedule," Novikov said. "There is no money, and it's impossible to keep construction works going without money." But Larijani said Tuesday that Iran expected Russia to stick to its obligations. "Russia has to fulfil its promises on time," the official news agency quoted Larijani as saying.