A small leak in a pool near the reactor caused a delay in starting up Iran's first nuclear power plant but it has now been fixed, a senior official was quoted as saying on Monday.

Ali Akbar Salehi, head of Iran's Atomic Energy Organization, also said the delay had nothing to do with the global Stuxnet computer virus believed mainly to have affected Iran.

Last week, Iranian officials said Stuxnet had hit staff computers at Bushehr, a symbol of Iran's growing geopolitical sway and rejection of international efforts to curb its nuclear
activity. But the virus had not affected major systems there, they said.

Security experts say the release of Stuxnet may have been a state-backed attack on Iran's nuclear program, most likely originating in the United States or Israel, which accuse the
country of seeking to develop atomic bombs. Iran denies this.

When Iran began loading fuel into Bushehr in August, officials said it would take two to three months for the plant to start producing electricity and that it would generate 1,000 megawatts, about 2.5 percent of the country's power usage.

But Salehi said last week the fuel would soon be transferred to the core of the reactor and the plant would begin supplying energy in 2011, signalling a delay in its start-up.

He gave further details on Monday, saying "a small leak was observed in a pool next to the reactor and was curbed," the official IRNA news agency reported.

Salehi added: "This leak caused the activities to be delayed for a few days. The leak has been fixed and the core of the reactor is working properly."

Mark Fitzpatrick, at the International Institute for Strategic Studies, said Salehi might have been referring to a pool for receiving spent fuel rods from the reactor.

He said this did not sound "very serious" but suggested that Iran may be downplaying any problems at the plant.

"Typically Iran exaggerates everything about their nuclear program in a positive way," Fitzpatrick said. "It could be more serious trouble than he has stated."

Iran's program includes uranium enrichment - separate from Bushehr - that Western leaders suspect is geared towards developing atomic bombs. Iran says it is refining uranium only
for a future network of nuclear power plants.

Diplomats and security sources say Western governments and Israel view sabotage as one way of slowing Iran's nuclear work.