Updated

Iran has received a new shipment of nuclear fuel from Russia for its first nuclear power plant, the official IRNA news agency reported Wednesday, a key step following the plant's recent startup.

The Russian-built Bushehr plant in southern Iran has been on the fringes of the controversy surrounding Iran's nuclear program. The United States and its allies suspected a connection between the plant and what the West believes are Iranian attempts to develop a nuclear weapon — a charge denied by Tehran.

Hamid Khadem Qaemi, spokesman for Iran's nuclear agency, said Russia delivered a total of 33 tons (30 metric tons) by plane over the last week for Bushehr. The amount is meant for the plant's second year of operation, IRNA quoted Qaemi as saying.

Bushehr's startup was repeatedly postponed and recently, foreign intelligence reports said the plant's control systems were penetrated by Stuxnet, a malicious computer software.

Iran maintained that Stuxnet was only found on several laptops belonging to plant employees and didn't affect the facility. Tehran later blamed the U.S. and Israel of being behind Stuxnet, saying the worm was part of a covert plan by Iran's enemies to sabotage its nuclear program.

The Bushehr project dates back to 1974, when Iran's U.S.-backed Shah Mohammed Reza Pahlavi contracted with the German company Siemens to build the reactor. The company withdrew from the project after the 1979 Islamic Revolution toppled the shah and brought hard-line clerics to power.

In 1992, Iran signed a $1 billion deal with Russia to complete the project and work began in 1995.

Under the contract, Bushehr was originally scheduled to come on stream in July 1999 but this was repeatedly delayed by construction and supply glitches.

Iran last year said that the much-delayed operation of the plant was to begin last December. Russia had already delivered 90 tons (82 metric tons) in eight shipments in 2007 and 2008, sufficient for a one-year consumption in Bushehr's 1,000 megawatt light-water reactor.

But in February, Russia ordered that fuel be removed because of concerns that metal particles might be contaminating fuel assemblies; reloading began in April.

The delays at Bushehr have hurt relations with Moscow and prompted Iranian officials to describe Russia as an "unreliable partner." Iran's state media have often said politics, not technical issues, are the reason behind them.

On Tuesday, Atomstroyexport, the Russian state company that built Bushehr, said the first reactor at the plant had gone into operation after a self-sustained fission reaction began Sunday.

Unrelated to Bushehr, Tehran has been slapped with four rounds on U.N. sanctions over its refusal to halt uranium enrichment and world powers are now trying to nudge Iran toward a compromise over the issue.

Low-enriched uranium can be used to fuel a reactor to generate electricity, which Iran says is the intention of its growing uranium enrichment program. But if uranium is further enriched to around 90 percent purity, it can be used to develop a nuclear warhead.