Iran will shortly resume nuclear fuel research, part of its controversial nuclear programme which had been suspended during talks with the EU.
Iran faces the threat of sanctions if it does not halt its nuclear plans
Mohammad Saidi, deputy head of Iran's Atomic Energy Organisation, said the research would be supervised by the International Atomic Energy Agency.
The announcement came as Iran said it would consider a proposal that it conduct uranium enrichment in Russia.
The US and EU do not want it to produce fuel suitable for use in nuclear bombs.
Iran has denied it is seeking to build nuclear weapons and says it is seeking only to produce electricity.
Mr Saidi announced on Iranian state television that Tehran had told the IAEA in writing that research work would resume within the next few days.
IRAN'S NUCLEAR STANDOFF
September 2002: Work begins on Iran's first nuclear reactor at Bushehr
December 2002: Satellite photographs reveal nuclear sites at Arak and Natanz. Iran agrees to an IAEA inspection
September 2003: IAEA gives Iran weeks to prove it is not pursuing atomic weapons
November 2003: Iran suspends uranium enrichment and allows tougher inspections; IAEA says no proof of any weapons programme
June 2004: IAEA rebukes Iran for not fully co-operating with nuclear inquiry
November 2004: Iran suspends uranium enrichment as part of deal with EU
August 2005: Iran rejects EU proposals and resumes work at Isfahan nuclear plant
"As our dear nation knows, about two and a half years ago our country agreed to voluntarily suspend research in nuclear fuel technology," he said.
"We think that during this period our experts incurred heavy losses and many of our researchers lost their jobs. For the same reason, it was decided to inform the IAEA today on the resumption of the research."
Mr Saidi stressed that the resumption of research did not mean that Iran would start to manufacture nuclear fuel.
"No decision has been made about nuclear fuel production," he added.
Earlier on Tuesday, Iranian Foreign Ministry spokesman Hamid Reza Asefi told reporters that Iran would talk to a Russian delegation about the latest proposal on its nuclear programme, before deciding whether to accept it.
"A Russian delegation led by Deputy Foreign Minister [Sergey] Kislyak, is due to come on 7 January to discuss the Russian proposal," he said.
Moscow suggested last year that Iran be allowed to conduct uranium enrichment in Russia, giving the country access to the nuclear fuel cycle while ensuring its nuclear program was for peaceful purposes.
Mr Asefi said the deal was ambiguous, and would only be acceptable to Iran if it was allowed to enrich uranium on its own territory too.