Russia will not send nuclear fuel to the Russia-building nuclear power plant in Bushehr, southwestern Iran, until disputes between the two sides were solved, Russian media reported on Tuesday.

"The project is at the stage of completion and certain difficulties have emerged. The general political background is not affecting this cooperation very constructively," the Itar-Tass news agency quoted First Deputy Foreign Minister Andrei Denisov assaying.

The Itar-Tass did not specify the difficulties but Russia has complained about the payment. A delegation from the key Russian contractor Atomstroiexport has left for Tehran to settle financial disputes.

The diplomat said Russia should offer nuclear fuel to the Iran's first nuclear power plant six month before the so-called "physical launch" according to a set plan.

But "first of all, disputed points must be resolved, then the acceptable date for that physical launch must be set, and then we will be able to talk about fuel supplies," the Interfax news agency quoted Denisov as saying.

More than 2,500 Russian specialists were now living and working in the suburb of Bushehr, the Itar-Tass cited sources with the Atomstroiexport.