Top nuclear negotiator Hassan Rowhani said Iran wanted to end a nine-month freeze on uranium conversion activities by Saturday.
Officials earlier suggested it hoped to restart the process on Wednesday.
Iran’s intention to resume uranium conversion, the precursor to enrichment, has caused grave concern in European countries.
The EU has the Tehran government that it could be hauled before the UN Security Council and face possible sanctions.
The latest manoeuvring came as new ultra-conservative President
Mahmood Ahmadinejad took office.
“We hope to resume (uranium conversion) by the start of next week,” Hassan Rowhani told state television. The week starts on Saturday in Iran.
Earlier, nuclear negotiator Ali Agha Mohammadi had said: “I hope to remove the seals and resume activities today.”
He was referring to seals placed by international nuclear inspectors on the Isfahan plant in central Iran.
However, there was still no sign that Iran was reconsidering its decision to resume conversion activities.
Instead it appeared to be merely adjusting its timetable in line with a call by the International Atomic Energy Agency (IAEA).
It remains to be seen what the future holds for the talks between Iran and the European Union, which saw the nine-month-old suspension of conversion as a key goodwill gesture from Tehran.
The EU Commission said relations between the European Union and Iran had reached a “critical stage”.
The United States accuses Iran of seeking to develop a nuclear bomb and talks between the EU and Iran have tried to reach a deal that would give Iran nuclear cooperation in return for guarantees that its atomic program was peaceful.
US officials said the Europeans would reveal their proposals, already dismissed by Iran as too little too late, at the weekend.