Investing.com - Oil Monday was near three-month lows as concerns about increased U.S. supply prevailed.
U.S. crude was off 13 cents, or 0.27%, at $48.36 at 08:00 ET after dipping below $48.
Brent crude shed 6 cents, or 0.12%, to $51.31.
Baker Hughes data Friday showed the number of rigs operating in the U.S. rose by 8 in the latest week to 617.
That was the eighth weekly increase in a row, with the count now at levels last seen in October 2015.
U.S. crude inventories currently stand at a record 528.4 million barrels.
Higher U.S. output could cancel out the impact of cuts by major producers.
OPEC and non-OPEC producers are pushing ahead with output cuts of 1.8 million barrels a day in the first half.
Investors will look to OPEC's monthly report Tuesday for an update on compliance with the cuts.