Ali Akbar Hashemi Rafsanjani said the U.S. has been pressuring Russia not to open the plant in southern Iran, which Tehran wants opened in September, after final testing of equipment.
"We hope that the Russian government will honor its obligations, and will not repeat the illogical delays to the final stage which have occurred in the past," Rafsanjani told the country's Assembly of Experts.
Iranian Energy Minister Parviz Fattah said on national television on Tuesday that the Bushehr plant would begin producing 500 MW of its 1 GW capacity of electricity by August 22, and would be brought up to full capacity by the end of March 2010.
Iran currently has about 32 GW of installed generating capacity, of which around 80% comes from natural gas.
The plant, which Russia's Atomstroyexport is completing under a 1998 contract, was originally scheduled to go on line at the end of 2006, but the date has been pushed back several times.
Iran has consistently denied Western allegations that its nuclear power program is aimed at building nuclear weapons.
In December 2007-January 2008, Russia supplied nuclear fuel for the plant under the 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 contractors. However, the companies stopped work after a U.S. embargo on hi-tech supplies to Iran was imposed following the 1979 Islamic Revolution and the seizure of the U.S. embassy in Tehran by radical students.