By Steve Rosenberg
BBC News, Moscow
The head of Iran's nuclear programme is holding talks in Moscow on expanding co-operation with Russia.
Russia and Iran plan further co-operation in nuclear energy
The visit of Gholamreza Aghazadeh, comes a week before a crucial meeting of the International Atomic Energy Agency (IAEA) in Vienna.
The meeting is due to decide whether to refer Iran to the United Nations Security Council for possible sanctions over its nuclear programme.
Iran has warned of "consequences" if Europe refers Iran to the UN.
In the eyes of the United States and the European Union, Iran is a threat - a country which they suspect of plotting to develop a nuclear bomb.
To Russia, though, Iran is a valued business partner. And at talks in Moscow, Russia and Iran have pledged to boost co-operation in the field of nuclear energy.
For a number of years, Russian engineers have been building an atomic plant at Bushehr, in southern Iran.
Russian officials have now promised the power situation will be up and running by the end of next year.
Iran resumed uranium conversion despite international pressure
Also, there is no sign of Moscow encouraging Tehran to stop uranium conversion - a controversial process which Iran resumed last month and which many in the West fear is part of a secret weapons programme.
Europe and Washington are threatening to seek Iran's referral to the UN Security Council for possible sanctions if the Iranian government does not call a halt.
Talks with the EU are unlikely, however, as Europe says Iran's decision last month to resume conversion of uranium violated the agreement underpinning months of negotiations.
But Russian Foreign Minister Sergei Lavrov hinted that Moscow would not support such a move. The minister said he believed there was still scope within the IAEA to resolve disagreements with Iran.