IRAN will fire up its first nuclear power plant next week in defiance of international pressure, marking an advance in its nuclear ambitions.

Russia, which built the Bushehr plant in Iran, confirmed that it would start loading nuclear fuel into the reactor next week, bringing the plant on line to feed nuclear-generated electricity to Iranian cities within a month.

“From that moment the Bushehr plant will be officially considered a nuclear-energy installation,” Sergei Novikov, a spokesman for the Russian nuclear agency, said.

Iran’s plans are likely to reignite the conflict between foreign powers over how to deal with the Ahmadinejad regime

The Russian move comes despite Western demands that all nuclear development in Iran be frozen until Tehran can prove that it is not seeking to build a nuclear weapon. In March Hillary Clinton, the US Secretary of State, warned Russia that it would be premature to bring Bushehr on line without Iranian assurances on its uranium-enrichment programme.

Iran continues to enrich uranium despite five UN Security Council resolutions calling on it to stop until the questions over suspected weapons work are resolved.

Inspectors from the International Atomic Energy Agency (IAEA), the UN nuclear watchdog, said that they discovered evidence suggesting a military dimension to the programme. Iran refused to address those specific questions, arguing that its nuclear programme was for civilian purposes only.

The Bushehr project began in 1995 when Russia signed a dollars 1 billion (pounds 640million) contract to build it. Moscow has dragged its feet on completing the project, citing technical reasons, but it is believed that it was using the project to pressure Iran not to defy the international community.

Russian anger over the discovery of a secret enrichment plant is credited with bringing Moscow round to backing UN sanctions in June. The Russians were said to be furious that Tehran had hidden the development of the plant. Its decision to back the sanctions proved crucial in winning support from China, which had feared the impact on its energy trade with Iran.

The sanctions agreed, however, were less punitive than those sought by the US and the EU, which followed up with additional measures against the Iranian banking and energy sectors.

Russia argued that the sanctions did not prevent it from going ahead with the Bushehr project. However, President Medvedev said this month that Iran was close to attaining the potential to build a nuclear weapon. It was the first time that a Russian leader had warned so explicitly of the dangers of Tehran’s nuclear drive.

Tehran has signed a contract with Moscow under which spent fuel from Bushehr will be sent to Russia for reprocessing, removing the risk that it could be diverted to make plutonium for a weapons programme.

Russia, which is keen to profit from the export of nuclear energy technology, argued that the Bushehr project was essential in persuading Iran to work with the international community, proving that the world was not trying to deny it a legitimate technology.

Iran sees the completion of Bushehr as an important milestone, not only in its nuclear programme but also as a symbol of defiance against the West.

The Bushehr project was begun under the Shah, with the help of German and French scientists. With the fall of the Shah in the 1979 Islamic revolution the project was halted, and damaged during the subsequent Iran-Iraq war. Russia signed the contract to reconstruct the plant in 1995.

Ali Akbar Salehi, the head of the Atomic Energy Organisation of Iran, said that the country had invited IAEA analysts to watch the transfer of fuel and the firing of the reactor at Bushehr next weekend.