Bushehr, Iran’s first nuclear power plant, will start switching to full capacity from May 23, Atomstroyexport, part of Russia's civilian nuclear power corporation Rosatom, said on Thursday.

"Currently, the plant is operating at a lower capacity. The stage of further increasing the capacity of the Bushehr nuclear power plant [from 75 percent to 100 percent] is scheduled to commence on May 23, 2012," Atomstroyexport said in a statement.

Under a bilateral agreement approved by the International Atomic Energy Agency, Russia will operate the plant, supply its fuel and take away all the spent fuel for the next two or three years, but will eventually hand over full control to Iran.

The construction of Bushehr took more than three decades and has been dogged by delays. Russia signed a contract with Iran in February 1998 to complete the plant, which German companies first began back in 1975.