"I promised to verify the timeframe for the construction of the Bushehr nuclear plant, but I can say with certainty that the plant will not be commissioned before the end of 2008," said Sergei Shmatko, the head of state-controlled Atomstroyexport,
Shmatko is currently visiting China, where Atomstroyexport has built a nuclear power plant in the eastern port city of Lianyungang under a 1992 agreement.
Russia announced the start of nuclear fuel deliveries to Iran's atomic power plant on Monday.
"Containers with fuel sealed by IAEA [International Atomic Energy Agency] inspectors have been delivered to the site and placed in a special storage facility subject to international safety monitoring," Russia's state nuclear power agency Rosatom said.
The start of deliveries followed months of delays to the plant's construction, which Moscow attributed to payment arrears, but Iran blamed on pressure from Western nations, who suspect the Islamic Republic of plans to build nuclear weapons.
The United States and other Western powers have pushed for measures to force Tehran to halt uranium enrichment, which is used in both electricity generation and weapons production.
Russia's Foreign Ministry said the start of nuclear fuel supplies to Iran means the country has provided additional written guarantees that the fuel will be used solely for electricity generation.
Under a Russian-Iranian agreement on Bushehr, nuclear fuel deliveries to the plant start about six months ahead of its commissioning. The ministry said supplies would continue into February 2008.
Spent Russian fuel is to be re-exported for reprocessing and storage, according to the agreement. In Iran, the nuclear fuel will be under control of the United Nations nuclear watchdog, the International Atomic Energy Agency, the ministry said.