The announcement came as Russia's Rosatom deputy chief Nikolai Spassky arrived in Tehran for a two-day visit during which he will meet senior nuclear officials.
Spassky will also meet Deputy Foreign Minister Abbas Araqchi, a senior negotiator in talks with world powers on Iran's nuclear ambitions, the official IRNA news agency reported, without elaborating.
Iran's Atomic Energy Organization spokesperson Behrouz Kamalvandi said after months of negotiations, the deal will be signed this week, the ISNA news agency reported.
Under a provisional agreement, Russia will build two more 1,000-megawatt plants next to Iran's sole existing plants in the southern Gulf port city of Bushehr.
No further details have been reported.
Oil-rich Iran says it wants to operate at least 20 nuclear power plants capable of producing 20,000 megawatts of electricity, as a way of decreasing dependency on its vast oil and gas resources.
"It is possible that in addition to the two nuclear power plants, we will also discuss further power plants," Kamalvandi added.
The Bushehr nuclear power plant that came online in 2011 uses Russian-provided fuel, and is not of international concern.
But Western powers in ongoing talks with Iran are seeking to ensure that its other controversial nuclear activities -- including enrichment of uranium -- are of a purely civilian nature, and that the Islamic republic will never be able to acquire an atomic bomb.
A new round of talks is scheduled for July 2 in Vienna, as Iran and the five permanent members of the UN Security Council plus Germany work to transform an interim deal into a lasting accord by a self-imposed July 20 deadline.
Under such an agreement, Iran's nuclear work will be curbed and subject to increased monitoring in exchange for the lifting of painful sanctions choking its oil-reliant economy.