Iran's Bushehr nuclear power plant will start reaching its full capacity from May 23 as scheduled, the plant's Russian contractor Atomstroyexport said in a statement on Thursday.

According to Atomstroyexport, Bushehr, the first nuclear power plant in Iran, has successfully reached 90 percent of its nominal capacity in routine trials in early May.

"Currently, the plant is operating at a lower capacity. The next stage of increasing Bushehr's capacity (from 75 percent to 100 percent) is scheduled for May 23, 2012," Atomstroyexport said in a statement.

Earlier, Russian officials said work at the Bushehr plant was proceeding as scheduled and they expected Bushehr could switch to full power in the first half of 2012.

Construction of the Bushehr plant was started in 1975 by several German companies. However, the work halted when the United States imposed an embargo on hi-tech supplies to Iran after the 1979 revolution. Russia signed a contract with Iran to complete the construction in 1998.

Completion of the plant's construction was postponed several times by mounting technical and financial challenges and pressure from the United States.