The head of the IAEA said his upcoming visit to Tehran could "pave the way" for a revival of the Iranian nuclear deal, an agreement that would return the country's oil exports to world markets, Bloomberg reported.

The optimism of the head of the IAEA, Rafael Grossi, was supported by diplomats in Vienna, where they discuss the last few outstanding issues.

Russian Ambassador Mikhail Ulyanov said that the parties are at the finish line and the deal is possible within 48 hours. Other negotiators have also said privately that they expect an agreement by early next week.

Iran has demanded that the International Atomic Energy Agency complete a stalled investigation into past nuclear activities as part of a deal to renew a 2015 deal that limited the Islamic Republic's nuclear program in exchange for sanctions relief.

Western negotiators have so far said that this is not possible because the IAEA operates independently and does not have the power to obstruct an investigation. But Grossi made clear in an interview with Bloomberg TV that while a number of issues needed to be cleared up before he could close the investigation, a deal could be reached.

The revival of the landmark nuclear deal with Iran, referred to as the Iranian deal, would mean relief for global energy markets. Oil rose to $116 a barrel amid Russia's war with Ukraine and the reluctance of other oil-producing countries to significantly increase production.

Traders expect Iranian barrels to return to world markets this year. With the world's second-largest natural gas reserves and fourth-largest crude oil reserves, Iran is likely to be able to increase exports by about 1 million barrels a day within months of any deal, traders said.

Grossi said negotiators are consulting with IAEA officials as the talks draw to a close. Diplomats warn that there are only a few days to salvage the agreement.