"We have managed to advance the pace of work on the Bushehr site, but several questions remain as to the guaranteed financing of the construction," Atomstroiexport head Sergei Shmatko said, according to the RIA Novosti news agency.

"The fate of the construction is practically in the hands of our Iranian customers at the moment," Shmatko said, adding that he hoped to find "a common language" at planned talks in Tehran later this month.

The power station in the Iranian town of Bushehr was initially scheduled to be launched this year, including the start of nuclear fuel shipments from Russia.

Moscow has delayed the launch, saying Tehran had stopped paying for construction.

Washington and its European allies accuse Iran of working to develop nuclear arms under the cover of a civilian energy program, while Tehran insists its only goal is generating electricity.