Oil prices fell on Tuesday ahead of a nuclear pact that could release more Iranian crude into the oversupplied market, although prices backed off session lows as the clock ticked towards the talks' self-imposed deadline set for the end of the day with no word of a deal.
Six world powers, consisting of the United States, Britain, France, Germany, Russia and China, ramped up negotiations with Iran in Switzerland for outline deal on Tehran's nuclear program that would be integral to removing sanctions on its oil exports.
Iranian oil exports have been limited to around 1 million barrels per day by the U.S.-led sanctions.
Tehran could raise output by around 500,000 bpd within six months if the restrictions are removed, and by an additional 700,000 bpd within another year, according to estimates by Facts Global Energy.
Oil prices have fallen around 7 percent since Thursday's close as fear Iran would achieve a pact with the world powers bringing more crude to a market already swollen with supplies.