The United States and its European allies are working on a new deal for a nuclear fuel swap with Iran, amid continuing concern over its nuclear ambitions.
A US State Department spokesperson says the revised offer will include tougher conditions. The last offer was rejected by Tehran.
The BBC reports the deal in 2009 was supposed to be a confidence building measure.
Iran was to ship out 1200 kilograms of its uranium stock to be enriched abroad.
This would have removed enough uranium from the country to allay fears about Iran's capacity to build a nuclear bomb and would have provided Tehran with the enriched uranium it needs for medical uses.
The new deal will take into account the increase in Iran's uranium stockpile and level of enrichment since then.
US officials have not commented on details of the offer, but reports suggest that Iran will be asked to ship out now close to 2000 kilos of uranium.
