Iran has begun loading fuel into its first nuclear power plant, moving closer to its opening in the face of Western fears over its eventual plans for weapons.
The government sees the completion of the plant, built with the help of Russia, as a show of defiance against UN Security Council sanctions against its nuclear programme.
A leak in a storage pool delayed the operation for months, but Iran has said the 1,000-megawatt nuclear plant will begin generating electricity in early 2011.
Originally there had been speculation that the delay was caused by a computer worm found on the laptops of several plant employees.
The US withdrew its opposition to the plant after Russia satisfied concerns over how it would be fuelled and the fate of the spent fuel rods.
Under a deal signed in 2005, Russia will provide nuclear fuel to Iran, then take back the spent fuel, a step meant as a safeguard to ensure it cannot be diverted into a weapons programme.
Iran has also agreed to allow the UN's nuclear agency to monitor the Bushehr plant and the fuel deliveries.
Worries remain, however, over Iran's programme to enrich uranium for nuclear fuel since the process can also be used to create weapons-grade material.
The United States claims that the fuel deal with Russia shows Tehran does not need uranium enrichment, but Iran maintains it will build other nuclear power plants and needs its own fuel source.
Iran is already producing its own nuclear fuel - uranium enriched to about 3.5%. It also has started a pilot programme of enriching uranium to 20%, which it claims is needed for a medical research reactor. Weapons grade material has to be enriched to 90%.