International Atomic Energy Agency (IAEA) spokesman Peter Rickwood said on Wednesday that the signing will take place at the nuclear watchdog's headquarters in Vienna on Thursday.
 
Iran's vice president and head of Tehran's atomic energy organisation, Gholamreza Aghazadeh, earlier signalled that the Islamic republic could sign the treaty.
  
Iran has come under mounting pressure, notably from the United States, to sign the text, amid accusations that it is using a civil atomic energy programme as a cover for secret nuclear weapons development. Tehran denies the allegation, saying its programme is for producing electricity.
  
Last month, the IAEA condemned Iran for 18 years of covert nuclear activities, although a report said there was no clear evidence the country had been developing nuclear arms.
  
IAEA Director General Muhammad El-Baradei has argued that the agency needs more powers as it continues to probe Iran, including the ability to carry out unannounced inspections of suspect nuclear sites-while Iran has been worried such inspections could violate national sovereignty.
  
Under the basic treaty, the IAEA is only authorised to carry out pre-arranged site inspections.
  
Iranian diplomats in Vienna on Wednesday said it was not clear yet which Iranian representative would sign the protocol.