Oil prices traded roughly flat after hitting three-month lows on Monday, as rising inventories and drilling activity in the United States, the world's top energy consumer, offset optimism over OPEC's efforts to restrict crude output and reduce a global glut.
After more than two months of reduced production from the Organization of the Petroleum Exporting Countries, the market is facing evidence that U.S. production remains high and global markets remain oversupplied.
On Monday, the Energy Information Administration forecast U.S. shale oil output from seven major production basins would increase by 109,000 barrels a day in April.
"There is growing skepticism that the production cut has been enacted long enough to take care of the overhang," said Gene McGillian, director of market research at Tradition Energy. "The longs who piled in last year are turning on the market because there seems to be a realization that a six-month agreement isn't long enough to rebalance the market.
U.S. West Texas Intermediate crude (WTI) ended Monday's session 9 cents lower at $48.40 a barrel, bouncing off an intraday low of $47.90.
Brent crude was up 1 cent on the day, at $51.38 a barrel by 2:37 p.m. ET (1837 GMT), having hit a session trough of $50.85, its lowest since Nov. 30.
Prices have fallen by more than 8 percent since last Monday, its biggest week-on-week drop in four months, and analysts said the slide may not have much further to run.
Goldman Sachs said in a note it remained "very confident" about commodity prices and maintained its price forecast of $57.50 a barrel for WTI in the second quarter.
The slide could be the result of traders unwinding bullish long positions, and could slow as those positions are unwound, Tradition Energy's McGillian said. Money managers cut their net long positions in U.S. crude futures and options in the week to March 7.
U.S. drillers added oil rigs for an eighth consecutive week, Baker Hughes data showed on Friday, and they have announced ambitious production growth plans as they rebound from a two-year price war with OPEC.
OPEC and other major oil producers including Russia reached an agreement late last year to rein in production by almost 1.8 million barrels per day (bpd) in the first half of 2017.
Russia's top oil major Rosneft warned that a recovery in U.S. oil output may deter OPEC and non-OPEC producers from extending production cuts beyond June and might lead to a new price war.
Meanwhile, Kuwait's oil minister on Monday said his country will support the extension of the global deal to cut oil supply beyond June.
Although OPEC states have been complying with supply curbs, led by Saudi Arabia, it has not been enough to overshadow a rise in U.S. inventories to a new high.
"It will be interesting to see how OPEC rhetoric will evolve with this price correction. Is price the only consideration when it comes to the decision of extending cuts?" BNP Paribas global head of commodity strategy Harry Tchilinguirian told the Reuters Global Oil Forum.
He added that OPEC's task was more difficult as it aimed to cut inventory levels rather than simply target a specific price.
Signs of potential supply disruptions emerged from Libya, one of two OPEC countries exempt from cutting output. Libya has raised production in recent months.
A senior official at Libya's National Oil Corporation (NOC) warned on Monday of a possible declaration of force majeure at the Es Sider and Ras Lanuf oil terminals, as air strikes continued and rival forces mobilized fighters in the area.
The violence in Libya's Oil Crescent has raised concerns of a new escalation of conflict in Libya between eastern and western based factions that have been competing for power since 2014.
— CNBC's Tom DiChristopher contributed to this report