Oil slipped more than 1 percent on Monday, as rising crude output with Libya hitting its highest production since 2014 and increased U.S. drilling countered OPEC-led production cuts aimed at clearing a supply glut.
Signs of slower-than-expected growth in manufacturing in China and a weaker figure for U.S. manufacturing sentiment also weighed on expectations for oil demand and the market.
U.S. crude for June ended Monday's trading down 49 cents, or 1 percent, at $48.84 a barrel. Global benchmark Brent crude for July was down 51 cents, or 1 percent, at $51.54 a barrel by 2:35 p.m. ET (1835 GMT).
"The market continues to hunt for a bottom," said Gene McGillian, manager of market research at Tradition Energy in Stamford, Connecticut.
U.S. crude has lost nearly 9 percent since April 11, weighed down by the market's impatience with the slow pace of inventory drawdown around the world even after major oil producers agreed late last year to cut production by 1.8 million barrels per day for the first half of 2017.