Iran says it has discovered a major new oilfield in the southwest of the country. That could increase its reserves by about a third. President Hassan Rouhani announced the discovery during a televised speech in the central city of Yazd. The field in the oil-rich Khuzestan province holds an estimated 53 billion barrels of crude. Iran already has the world's fourth largest reserves of oil. It's a vital oil trade has come under renewed pressure since the United States violated the 2015 nuclear deal and reimpose sanctions.