The plant in south Iran, which Russia undertook to finish as part of a 1998 contract, was originally scheduled to go on line at the end of 2006, but the date has been pushed back several times.
"We can say that the basic construction and assembly work has been completed at the NPP, and we are now switching over to start-up operations," Rosatom chief Sergei Kiriyenko said.
He said that under the Russian-Iranian contract, Russian experts will operate the plant's first reactor and have the task of creating a team of skilled Russian staff.
Foreign Minister Manouchehr Mottaki said earlier the Bushehr plant would go on stream in the first half of 2009. A Russian deputy foreign minister said last Friday the plant would be commissioned according to the schedule agreed on with Tehran.
In December 2007 - January 2008, Russia supplied nuclear fuel for the plant under control of the International Atomic Energy Agency (IAEA), the UN nuclear watchdog. Iran has agreed to return spent nuclear fuel to Russia.
The construction of the Bushehr plant was started in 1975 by German companies. However, the German firms stopped work after a U.S. embargo on hi-tech supplies to Iran was imposed following the 1979 Islamic Revolution and the subsequent take over of the U.S. embassy in Tehran.