"It is likely that the deadline for the Bushehr nuclear power plant completion will be slightly delayed despite the existing construction schedule. And I am not denying this," Hassan Qashqavi told journalists.
He added that the delay has been caused by "technical difficulties" that have no relation to the "political will of the Iranian and Russian leadership."
"We are satisfied by how Russia is implementing the project," Qashqavi said.
Iran's first nuclear power plant was originally scheduled to go into operation in late 2006, but the launch date has been postponed several times. Russia has cited financial problems, with Iran accusing it of caution amid suspicions by Western powers that Tehran could be seeking nuclear weapons.
The Islamic Republic has insisted it needs its nuclear program to provide civilian energy.
Iran's Atomic Energy Organization had said earlier the Bushehr plant was 94.8% complete. Foreign Minister Manouchehr Mottaki said it was due to be put into operation in the first half of 2009.
The president of Atomstroyexport, Russia's nuclear power equipment and service export monopoly, said in September that work due to be carried out in December-February would make its launch "irreversible."
Russia delivered its eighth and final nuclear fuel shipment to Bushehr in January, supplying a total of 82 metric tons of low-enriched uranium for the plant's light-water reactor.
The deputy head of Iran's Atomic Energy Organization, Mohammad Qannad, said on Sunday Iran, currently suffering from an electricity shortage, was planning to build another five nuclear reactors in the next five years.
