RIA Novosti quoted Iran's vice president and head of its atomic energy organization, Gholamreza Aghazadeh, as saying in Tehran that the accord would be signed during a visit by Russian Atomic Energy Minister Alexander Rumyantsev.

"During the upcoming visit of Russian Atomic Energy Minister Alexander Rumyantsev we will sign this document," Aghazadeh said. According to officials in Moscow quoted by the news agency, the visit will take place at the end of January.

Moscow and Tehran for the past year have been preparing an agreement under which Iran pledges to return all spent fuel used in the nuclear power reactor that Russia is building at Bushehr, in the southwest of the country.

But Russia has dragged its feet, insisting that Iran first sign a protocol allowing UN inspectors to stage surprise inspections of suspect nuclear sites.

The UN's nuclear watchdog announced earlier Wednesday that Iran would sign the additional protocol on Thursday at the International Atomic Energy Agency (IAEA) headquarters in Vienna.

Russia has been under pressure from the United States to call off its collaboration with Iran in the civil nuclear sector as Washington believes this to be a cover for developing nuclear weapons -- charges Tehran denies.

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