Oil prices fell on Thursday as amid concerns of oversupply to the market.
US crude inventories rose by 14.3 million barrels last week, industry data showed, more than four times higher than analysts' expected.
Meanwhile, some analysts have predicted that output from the world's largest oil producer Saudi Arabia could reach 10 million barrels per day.
The estimate would fit a pattern that suggest Riyadh is more concerned with protecting its market share than boosting oil prices via a production cut.
The US Energy Information Administration (EIA) is due to announce official weekly results later on Thursday. If inventories rose by the 14.3 million figure reported by the American Petroleum Institute, it would be the biggest weekly growth in production since records began.
US oil fell to $50.09 a barrel on Thursday, while Bent crude reached $58.86 a barrel, down from Tuesday's two-month high of $63 a barrel.