Iran's top nuclear negotiator has said Tehran will review its ties with the IAEA unless Russian changes to a UN draft resolution on Iran are accepted.
Mr Larijani is holding talks with a number of high-ranking officials
Ali Larijani made the threat of reduced co-operation with the UN's nuclear watchdog before he began talks in Moscow on Iran's nuclear policies.
A resolution drafted by the UN Security Council's three EU members threatens sanctions over Iran's nuclear efforts.
But Russia says the text is too tough and is seeking a watered down version.
"We will review our relations with the IAEA if the UN accepts the Euro-troika resolution without taking into account the amendments made by Russia," Mr Larijani, the secretary of Iran's Supreme National Security Council, was quoted by Interfax news agency.
'Work to continue'
Mr Larijani warned that even if the Russian changes to the draft are not included, the UN resolution "will not make Iran change its mind" about its nuclear programme.
Iran says its enrichment work is aimed at generating electricity, but the US and other Western nations fear Iran is trying to acquire nuclear weapons.
"We have to find a logical way to solve this problem," Mr Larijani said.
On Friday, Mr Larijani held talks behind closed doors with Russian Foreign Minister Sergei Lavrov.
Mr Lavrov said before the meeting that Moscow "invariably advocates a negotiated solution" to Iran's nuclear problem, Itar-Tass news agency reported.
Mr Larijani later began talks with the head of the Russian national security council, Igor Ivanov.
Russia, which has the power to veto UN Security Council resolutions, has significant economic ties to Tehran and is resisting any restrictions on its work to build a new nuclear reactor at Bushehr in Iran.
According to the RIA Novosti news agency, Mr Larijani also said that a Moscow proposal that it enrich uranium in Russia for Iran is still being considered.
"This proposal was never rejected and it remains on the negotiating table," the news agency quoted him as saying.
In October, Iran stepped up work to enrich uranium by activating a second cascade of centrifuges at its Natanz plant.
Feeding gas into centrifuges can produce fuel for nuclear power plants or, ultimately, atomic weapons.
The move was seen as an act of international defiance by Tehran, given demands by the UN Security Council that it suspend uranium enrichment.