Russia refused to launch the plant near the southern town of Bushehr until Iran agreed to return all of the nuclear fuel provided for the plant by Russia.

Like Washington -- which had fought furiously to convince Russia against the project -- Moscow feared that Tehran could reprocess the material to make a nuclear weapon.

Iran initially refused to sign the fuel deal sighting the dangers of transporting radioactive material back to Russia but Moscow refused to budge.

The two sides finally made headway last month and Russia is now on track to launch the 800-million-dollar (606-million-euro) project at the start of next year.

"The agreement on the return of nuclear fuel will be signed on Saturday," Rumyantsev's spokesman Nikolai Shingaryov told AFP.

Rumyantsev will visit Bushehr itself on Sunday and meet with his Iranian counterpart to "discuss wider cooperation in the nuclear sphere," the spokesman said.

Russia has examined the option of building a second reactor at Bushehr along with new nuclear plants at other locations.

The West argues Iran has no need for nuclear energy because of its massive oil supplies. However Tehran counters that its oil wells are actually far removed from the population while the pipeline network remains underdeveloped.

In Bratislava on Thursday, Russian President Vladimir Putin and his US counterpart George W. Bush agreed during summit talks that Iran must not have a nuclear weapon.

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