Oil dropped below $58 a barrel as investors weighed an increase in U.S. drilling rigs against OPEC's promise to extend output cuts through the end of next year.
Futures fell as much as 1.3 percent in New York after adding 1.7 percent Friday. OPEC and its allies including Russia last week agreed to keep supply cuts in place and beefed up the extension with the inclusion of Nigeria and Libya. Executives from three of the biggest independent U.S. drillers said that while they won't increase activity just because prices rise, they'll still grow.
Oil has advanced for the past three months amid optimism that output cuts by the Organization of Petroleum Exporting Countries and its partners are helping to balance the market. Yet U.S. rivals have been expanding their operations, with drillers adding two oil rigs to reach 749 last week, the highest level since late September, according to Baker Hughes.
"The OPEC deal will mostly work for non-OPEC," said Eugen Weinberg, head of commodities research at Commerzbank AG in Frankfurt. "Even if OPEC delivers the cuts promised, and prices stay high long enough, the main result will be that U.S. shale adds on close to 1 million barrels a day of additional production."
West Texas Intermediate for January delivery dropped 56 cents to $57.80 a barrel on the New York Mercantile Exchange at 1:44 p.m. London time, after gaining 96 cents on Friday. Total volume traded was about 16 percent below the 100-day average.
Brent for February settlement dropped 56 cents to $63.17 a barrel on the London-based ICE Futures Europe exchange. Prices added $1.10, or 1.8 percent, to close at $63.73 on Friday. The global benchmark crude was at a premium of $5.35 to February WTI.
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Pioneer Natural Resources Co., Parsley Energy Inc. and Newfield Exploration Co. said that, while they plan to grow, their emphasis will be on maintaining spending discipline and generating profit, rather than just boosting supply on higher oil prices. Pioneer plans to raise output to more than 1 million barrels of oil equivalent a day by 2026 from about 300,000 a day this quarter.
Money managers have increased their bullish ICE Brent crude bets by 11,739 net-long positions to 537,979, the most bullish level in three weeks, ICE Futures Europe data on futures and options show. Citigroup remains bearish on 2019, with a forecast of about $49 a barrel for Brent as OPEC, the U.S., Canada, Brazil and Russia look to add supply, and probably at a faster growth rate than demand, analysts said. Saudi Energy Minister Khalid Al-Falih said in Riyadh that OPEC and its partners won't pause in cutting supply until the market is balanced again.