Iran expects the sanctions to be suspended based on the Joint Comprehensive Plan of Action (JCPOA), the text of the nuclear deal finalized on July 14.
Iranian President Hassan Rouhani announced on Wednesday that the anti-Iran sanctions will be terminated in the Iranian month of Dey, which begins on December 22.
International Atomic Energy Agency (IAEA) Director-General Yukiya Amano, whose agency must verify that Iran has put the required nuclear restrictions in place for sanctions to be lifted, told Reuters that deadline could be met.
"If everything goes well, it is not impossible," he said in an interview when asked if so-called Implementation Day, on which IAEA verification and the lifting of sanctions are both supposed to take place, could occur by the end of January.
Iran said after an IAEA board meeting on Tuesday that it hoped to have put the required restrictions in place within two to three weeks. Amano has said his agency would then need a matter of weeks to verify the curbs.
On Wednesday, Amano confirmed that Iran was moving quickly to keep its side of the deal with the Group 5+1 member states- Russia, the United States, France, Britain, Germany and China.
"Our inspectors are on the ground and they are observing their activities, and with their report I can tell that Iran is undertaking activities at a very high pace," Amano said, though he declined to provide details on those activities.
"If your question is that Iran is planning to complete their preparatory activities in two, three weeks' time, I don't have a reason to doubt it," he said.
"If everything goes well it can go very smoothly, but if there's some mishandling it will take more time," he said. "It's difficult to say."
Amano, who has headed the IAEA for six years, would also not be drawn on how long the agency would need for its verification, beyond that it would take weeks rather than days or months.
"If there are some small things, we need to do it again and it will take time," he said. "If everything goes well, it will be smooth. It's like any complicated endeavor."
The IAEA's 35-nation Board of Governors decided on Tuesday to end its investigation of Iran's past nuclear-related activities, passing a resolution closing the matter by consensus, which means unopposed.
The move was a necessary stage for the enforcement of the lasting nuclear deal between Iran and the Group 5+1 (also known as the P5+1 or E3+3).
The landmark accord was achieved in Vienna on July 14 and was officially adopted on October 18.