The new commissioning date of October 2006 was marked on a document shown at a press conference given by project manager Assadollah Sabouri.
He said the process of starting up the reactor would take seven months from when the Russians hand over the keys, giving a start date in the first months of the year and would be totally operational by October of the same year.
Sabouri pointed out that Iran had until the end of 2005 to reach an agreement with th Russians over fuel for the plant. "The final date for delivery of the fuel is in the last few months of 2005", otherwise the start-up would be further delayed, he said.
"The contract for the return of spent fuel is something very complicated, there is no signing date as we are still negotiating," he added.
Delivery of the Russian fuel has been delayed as Moscow has bowed to pressure from the United States, who believe it could be used for military purposes.
Both the US and Israel are convinced that, under cover of producing nuclear power, the Islamic republic is secretly developing an atomic bomb, something Tehran strenuously denies.
The IAEA governing body will consider the question of Iranian nuclear power projects at a meeting at its headquarters in Vienna in September.
Iran, which has repeatedly claimed its nuclear programme is entirely for civil purposes, believes it has given sufficient assurances and is demanding that the issue be left off the IAEA agenda.
However, far from agreeing, the IAEA demanded further cooperation from Iran at its June meeting to provide conclusive proof that it is not secretly developing nuclear weapons.
Iran intends to produce its own fuel for the next stage of its nuclear programme after making "important advances" in its production, Sabouri said.
"Important advances have made, it will not be many years before we are in a position to produce our own fuel," he said.
Iran's ability to master the urnaium enrichment cycle is a cause for concern in the international community and the IAEA has expressed reservations that Iran could use the technology to produce its own bomb.
As a gesture of good faith, Iran agreed last year to suspend enriching uranium used for nuclear fuel but has always insisted that it was a temporary measure.
"Our programme is very clear," Sabouri said. "For the first stage we have a contract with the Russians for the supply of fuel for 10 years."
But he added: "We are counting on the fact that the second phase will use fuel produced by Iran."
In addition to the current nuclear plant at Bushehr, Iran plans six other stages of nuclear development, at Bushehr and elsewhere, to arrive at a producion of 7,000 megawatts of electricity by 2020.
Although the Russians are considered favourites to land the contract for the second phase, no deal has yet been signed.