Sanctions imposed on Iran could be lifted with the International Atomic Energy Agency (IAEA) expected to certify that Tehran has kept its promise and curbed its nuclear ambitions under the deal signed with six global powers last July. The lifting of the sanctions will see some $100bn (£70bn) worth of frozen assets in overseas banks being sent back to Iran and open up trade for Iranian oil.
"All parties have continued making steady progress towards implementation day of the JCPOA [Joint Comprehensive Plan of Action], which will ensure the exclusively peaceful nature of Iran's nuclear programme," US State Department spokesman Mark Toner said.
The UN nuclear watchdog is expected to come out with its report on 16 January, the Wall Street Journal cited western and Iranian officials as saying. "Almost all details are ironed out," a source told Reuters.
Also, on 16 January, US Secretary of State John Kerry is scheduled to meet Iran's Foreign Minister Mohammad Javad Zarif and EU foreign policy chief Federica Mogherini in the Austrian capital Vienna to discuss the Iranian nuclear deal.
Referring to the return of billions of dollars in frozen assets to Iran, Saudi Arabia's Foreign Minister Adel al-Jubeir said: "Every country in the world is worried about this. The concern in most countries is that Iran not use these funds in order to fund destabilisation activities, but instead use the funds to improve the well-being of its people."
The US has said that Iran curbing its nuclear ambition under the landmark nuclear deal would be a major step in stopping the spread of nuclear weapons.
Iran had signed the deal with United States, Russia, China, Britain, France and Germany.