The reported statement, which did not give a specific time for the launch of Bushehr, came as Iran's government announced plans to build 10 new uranium enrichment plants, in a major expansion of its disputed nuclear program.
Russia said in mid-November that technical issues would prevent its engineers from starting up the reactor at Bushehr by the end of the year as previously planned.
Moscow, which is under Western pressure to distance itself from Tehran over its nuclear activities, stressed at the time that politics had nothing to do with the decision.
"Russia will complete the Bushehr nuclear power plant at the earliest (possible) time," IRIB quoted Russian Energy Minister Sergei Shmatko as saying after talks with Iranian Oil Minister Massoud Mirkazemi in Tehran.
"The quick completion of the Bushehr power plant is the most important issue for both the Iranian and Russian atomic energy organizations and technical steps in this regard are under way based upon the scheduled plans," he said.
Shmatko, who also held talks with other senior Iranian officials, said the Bushehr project had become "a symbol of cooperation between Iran and Russia and nobody dares to hurt it," IRIB added.
Russia's nuclear chief Sergei Kiriyenko said in February that the Bushehr launch was scheduled for 2009.
Western powers suspect that Iran is seeking to build nuclear bombs. Iran, the world's fifth-largest oil exporter, denies this and says its nuclear program is aimed at generating electricity.
Shmatko also discussed other areas of energy cooperation with Mirkazemi, as well as oil prices and crude output by the Organization of the Petroleum Exporting Countries (OPEC) and non-OPEC producers, IRIB reported, without giving details.
Iran is a member of OPEC, but Russia is not.
"Bilateral cooperation in oil, gas and petrochemical industries ... was among the topics discussed in today's meeting," Mirkazemi was quoted as saying.
"Having cooperation from the Caspian Sea to the South Pars gas field, could be helpful in continuation of bilateral cooperation," he said.