Oil prices slipped Tuesday as traders estimated a key report will show another increase in US crude inventories that already are at record levels, exacerbating the global oversupply.
US benchmark West Texas Intermediate for April delivery fell 17 cents, closing at $49.28 a barrel.
In London, Brent North Sea crude for April, the global benchmark, closed at $58.66 a barrel, down 24 cents from Monday's closing level.
Both futures contract had fallen sharply on Monday and Friday as traders worried about abundant global supplies amid slower economic growth, with no sign of a slowdown in rising US crude stockpiles.
On Wednesday the US Department of Energy issues its weekly report on US crude and product stocks.
"We'll probably have another build in US inventories" that will put downward pressure on prices, said James Williams of WTRG Economics.
Experts polled by Bloomberg News project inventories to have risen by 3.75 million barrels last week, from 425.6 million barrels total the previous week.
Globally, crude supplies were boosted as oilfields in eastern Libya resumed pumping to the port of Hariga after a pipeline was repaired.
"The partial return of supply from Libya is weighing on the Brent price despite its sustainability being anything but certain," said Commerzbank analysts in a note to clients.
Crude prices have fallen more than 50 percent since June. Prices have risen off their January lows following a slowdown in US drilling activity, but analysts say the volatility is likely to continue for some time.
"It is apparent by now that drilling in the US will slow, global production growth is expected to be lower, and demand, at least in the US, is reacting positively to lower prices," British bank Barclays said in a report.
"In short, the market is forecast to remain oversupplied for most of 2015, but expectations beyond that are for more balanced fundamentals."