TEHRAN: Iran is to launch its first nuclear power reactor next week, the Islamic republic and Russia which helped build the plant said on Friday after years of delays to the highly sensitive project.

"We are preparing to transfer the fuel inside the plant next week ... Then we will need seven to eight days to transfer it to the (core of the) reactor," said Iran`s atomic energy chief, Ali Akbar Salehi.

"On August 21, the fuel will be transferred inside the building in which the engine" of the Bushehr power station in southern Iran is located, he said, quoted by Iran`s Fars news agency.

Salehi added that Iran had invited inspectors from the Vienna-based UN nuclear watchdog, the International Atomic Energy Agency, to attend the launch ceremony.

"The fuel is sealed and IAEA inspectors must be present to remove them," he said.

The rest of the fuel is to be transferred to the reactor`s core on September 5, Salehi said, according to Mehr.

It would take two more weeks for the reactor to reach 50 percent of its power generation capacity, allowing it then to be linked to the national electricity grid, the atomic chief added.

"It will take six to seven months to reach the maximum power level of the plant," Salehi said.

Salehi`s comments came soon after Russian atomic agency Rosatom said the Bushehr plant would be launched at a formal ceremony on August 21, although Rosatom officials gave a slower operational startup schedule.

"The fuel will be charged in the reactor on August 21. From this moment, Bushehr will be considered a nuclear installation," Rosatom spokesman Sergei Novikov said. "This can be considered as the physical launch."

Russia has been building the plant since the mid-1990s but the project was marred by a series of delays, and the issue is hugely delicate amid Tehran`s standoff with the West and Israel over its nuclear programme.

The UN Security Council hit Tehran with a fourth set of sanctions on June 9 over its nuclear programme, and the United States and European Union followed up with tougher punitive measures targeting Iran`s banking and energy sectors.

Officials in Russia said the launch would be marked at a ceremony in Bushehr attended by the head of Rosatom, Sergei Kiriyenko, his Iranian counterpart Salehi and possibly the Russian energy minister.

Ties between Moscow and Tehran have cooled over the past months as Russia toughened its line on the Iranian nuclear drive, but Prime Minister Vladimir Putin this year confirmed the plant would start up in summer.

Western countries accuse oil-rich Iran of seeking to acquire a nuclear weapon under the guise of its civilian nuclear programme.

But Tehran insists the drive is entirely peaceful and that it needs nuclear energy for a rapidly expanding population whose fossil fuels will eventually run out.

Rosatom officials emphasised it would still take time for the 1,000 MW capacity power plant to start significant work, with the facility working at a minimal power of one percent after three-four months.

Under the contract between Russia and Iran, Moscow has already sent the nuclear fuel for the plant, with Iran committed to send spent fuel back to Russia for reprocessing.

Russia in late 2007 and early 2008 delivered to Iran a full consignment of 82 tonnes of nuclear fuel, which has since been stored and sealed under UN nuclear agency safeguards.

President Dmitry Medvedev said earlier this month that Iran was close to attaining the potential to build a nuclear weapon, the first time a Russian leader had warned so explicitly of the dangers of the nuclear drive.

But Russian officials have always pointed out Iran has a right to the use of peaceful nuclear energy.

The project to build the plant was first launched by the late shah of Iran, Mohammad Reza Pahlavi, in the 1970s using contractors from German firm Siemens. But it was shelved when he was deposed in the Islamic revolution of 1979.

It was revived after the death of revolutionary founder Ayatollah Ruhollah Khomeini in 1989, as Iran`s new supreme leader Ali Khamenei and his first president Akbar Hashemi Rafsanjani emerged as supporters of the project.

In 1995, Iran won the support of Russia which agreed to fuel the plant as well as complete construction.

BDST: 2032 HRS, 2010, August 13, 2010