Iran's top nuclear negotiator has arrived in Moscow for talks with the Russian security chief, amid an international row over its programme.
Iran could face sanctions if it is brought before the UN
They are expected to discuss Russia's proposal that Iran enrich uranium in Russia, in a bid to ease controversy.
Next week, the UN nuclear watchdog, the IAEA, is to discuss whether to refer Iran to the UN Security Council, which has the power to impose sanctions.
Iran insists the programme is solely aimed at meeting its energy needs.
However, Western countries suspect that Tehran may be seeking to develop nuclear weapons.
Talks stalled after Iran resumed uranium enrichment research earlier this month.
Iran is said to have expressed interest in Moscow's proposal to enrich uranium on Russian soil, which was first made but rejected last year.
IRAN'S NUCLEAR STANDOFF
Sept 2002: Work begins on Iran's first reactor at Bushehr
Dec 2002: Satellites reveal Arak and Natanz sites, triggering IAEA inspections
Nov 2003: Iran suspends uranium enrichment and allows tougher inspections
June 2004: IAEA rebukes Iran for not fully co-operating
Nov 2004: Iran suspends enrichment under deal with EU
Aug 2005: Iran rejects EU plan and re-opens Isfahan plant
Jan 2006: Iran re-opens Natanz facility
Ali Larijani's talks with Russian Security Council chief Igor Ivanov and other officials come amid continuing international diplomacy over the nuclear programme.
The UN's International Atomic Energy Agency (IAEA) is due to meet on 2 February, when Western nations say they will seek to have Iran referred to the Security Council for possible sanctions.
China has said it is studying that proposal, but believes the dispute can still be solved by diplomatic means.
Iran has warned that a referral would prompt it to forge ahead with a full-scale uranium enrichment programme.
Washington, Israel and many European powers distrust Iran, partly because it had kept its nuclear research secret for 18 years before it was revealed in 2002.
Israel has warned Iran that the country will not accept an Iranian nuclear capability and has the "capacity to defend", if Iran retains its programme.
Western countries are concerned because the process of enrichment could ultimately be used both to generate electricity and to make nuclear weapons.