TEHRAN, Iran — Iran has discovered an oil field in the country’s south with more than 50 billion barrels of crude oil, its president said on Sunday, a development that could bolster the nation’s proven reserves by a third as it struggles to sell energy abroad.
The announcement by President Hassan Rouhani comes as Iran faces crushing American sanctions imposed last year when the United States withdrew from nuclear deal with Iran and world powers.
Mr. Rouhani, who made the announcement in a speech in the desert city of Yazd, said the field was in the southern province of Khuzestan, home to its crucial oil industry. Some 53 billion barrels would be added to Iran’s proven reserves of 150 billion, he said.
“I am telling the White House that in the days when you sanctioned the sale of Iranian oil, the country’s workers and engineers were able to discover 53 billion barrels of oil,” Mr. Rouhani said, according to the semiofficial Fars news agency.
The discovery could not be independently verified.
Oil reserves refer to crude that is economically feasible to extract. Figures can vary wildly by country because of different standards, though it remains a yardstick of comparison among oil-producing nations.
Iran has the world’s fourth-largest proven deposits of crude oil and the world’s second-largest deposits of natural gas. It shares a massive offshore field in the Persian Gulf with Qatar.
The new oil field could become Iran’s second-largest field, after one in Ahvaz with 65 billion barrels. The field is 925 square miles, with the deposit some 260 feet deep, according to the semiofficial Tasnim news agency.
The other countries involved in the 2015 nuclear deal — Germany, France, Britain, Russia and China — have been struggling to save it. But they have not offered any means by which Iran can sell its oil abroad.
Iran has since gone beyond the deal’s stockpile and enrichment limits, and started using advanced centrifuges barred by the deal. It has also begun injecting uranium gas into centrifuges at an underground facility.
The collapse of the nuclear deal coincided with a tense summer of mysterious attacks on oil tankers and Saudi oil facilities that the United States blamed on Iran.
Tehran denied the accusation, though it did seize oil tankers and shoot down an American military surveillance drone in June that brought the United States to the brink of launching strikes.