Global crude oil prices slipped, as signs of growing U.S. production outweighed optimism that many other producers, including Russia, were adhering to the agreement to decrease supplies.Brent crude oil futures fell more than one dollar, or 1.8 percent, to 56.09 dollars a barrel. U.S. crude was down one dollar, at 52.99 dollars a barrel. Analysts said the optimism surrounding OPEC and non-OPEC production cuts was being counterbalanced by fears of higher U.S. crude output.
Last week, U.S. energy companies added oil rigs for a 10th week in a row. This extended a recovery in activity into the eighth month, as crude prices remained at levels at which many drillers can operate profitably. This raised concerns that U.S. production is increasing and undermining efforts by OPEC and others to cut output. Rising exports from Iran also added to bearish sentiment.