Iran had an estimated 157 billion barrels of proved crude oil reserves in January 2018, the EIA website said.
In an address to a gathering of people in Iran's central city of Yazd on Sunday, Rouhani said a huge oil field has been recently discovered in the southwestern province of Khuzestan.
It still remains to be seen whether Iran will benefit from the oil, as it has struggled to sell its fossil fuels in the wake of the US's unilateral sanctions.
Two months after Reuters first reported that samples taken at the site had shown traces of uranium, the IAEA on Wednesday told member states at a closed-door briefing that it had found uranium traces at a site in Iran it did not name, but diplomats at the meeting said it was clearly the same place.
Iran now has the world's fourth-largest proven deposits of crude oil and the world's second-largest deposits of natural gas.
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The government says it is enacting reforms but has offered nothing that is likely to satisfy most protesters. Authorities had imposed an internet blackout for two weeks last month, later loosening it.
In comments in April, Leader of the Islamic Revolution Ayatollah Seyed Ali Khamenei said the US' attempts to block the export of Iranian oil will get nowhere as Tehran will be exporting any amount of crude it needs and wants. It shares a massive offshore field in the Persian Gulf with Qatar.
The new oil field could reportedly become Iran's second-largest field, following the one containing 65 billion barrels in Ahvaz city. However, they've offered no means by which Iran can sell its oil overseas.
Company or governments that buy Iran's oil face harsh USA sanctions.
But Iran began 4.5% enrichment in part to supply Bushehr despite the deal limiting it to 3.67%.
Rouhani said: "If we save the nuclear deal, Iran's arms embargo will be lifted and we can buy weapons or sell our weapons to the world".