Iranian Foreign Ministry spokesman Mohammad Ali Hosseini earlier said a series of cooperation deals and memorandums of understanding were to be signed in the Russian capital.
Mottaki visited Moscow in mid-September, when he met with Sergei Kiriyenko, the head of Russia's state nuclear agency, and discussed Iran's first nuclear power plant Bushehr, being built by Russia.
The $1 billion project in southern Iran suffered repeated delays, which Moscow attributed to payment arrears, but Tehran blamed on Western pressure.
Many Western leaders still suspect Iran of seeking to build nuclear weapons despite last week's U.S. intelligence report to the contrary.
Tehran is currently subject to two sets of UN Security Council sanctions over its defiance to halt uranium enrichment, needed in both weapons and nuclear electricity production. Iran insists it is after electricity generation.
However, during his visit to Tehran in October Russian President Vladimir Putin assured that Russia would complete the construction of the Bushehr plant.
During a November 26-30 inspection at a Siberian chemical plant, experts from the International Atomic Energy Agency (IAEA) and Russian nuclear specialists checked and sealed nuclear fuel containers set for delivery to Iran.
Russian officials said the fuel would be dispatched once it was required and the relevant instructions were received, but gave no exact date.
A further round of tougher sanctions for Iran, pushed for by the United States, has so far been blocked by Russia and China, which have strong business interests in the oil-rich nation.
