The European Union has submitted to Iran a set of proposals aimed at ending the crisis over its nuclear programme.
Iran has threatened to resume work at its Isfahan nuclear plant
The plan - which has not been made public - is said to involve recognition of Tehran's right to nuclear power in return for a number of guarantees.
Iran is considering its response, but a senior official said the government remained committed to resuming uranium enrichment activities next week.
They were suspended in November as a result of international pressure.
But last week Iran said work at the uranium conversion plant near Isfahan would start again on Wednesday, and cited lack of progress in talks with the UK, France and Germany.
The three EU countries have called an emergency meeting of the UN's nuclear agency, the IAEA, on Tuesday. The agency could refer the matter to the UN Security Council.
Iran says its nuclear programme is peaceful, but Western countries suspect its programme is a front hiding efforts to build atomic bombs.
The three EU countries are said to have offered recognition of Iran's right to produce nuclear power, as well improved trade relations with the EU, and guarantee of alternative nuclear fuel sources from Europe and Russia.
In return the Europeans reportedly insist that Tehran should permanently give up nuclear enrichment and construction of a heavy-water reactor - something the Iranians have rejected.
But the BBC's Frances Harrison in Tehran says there is no new incentive on the table, and it is highly unlikely Iran will accept these proposals.
"We will review this proposal today and tomorrow, and will definitely give our answer by Sunday," Iranian negotiator Hossein Mousavian told Reuters news agency on Friday.
Asked if Iran would still resume uranium conversion, he said: "Yes, definitely."
French Foreign Minister Philippe Douste-Blazy said: "I hope that Iran will hear the voice of reason and that it will take the path of negotiation and dialogue, and that it will not move toward a resumption of nuclear activities.
"We are even ready to support a civilian, but of course, non-proliferating, nuclear programme," he told France's Europe-1 radio.