Investing.com - Oil was lower Monday as a slowdown in Chinese manufacturing activity in April weighed on the demand outlook.
U.S. crude was off 27 cents, or 0.55%, at $49.06 at 04:45 ET.
Brent crude shed 32 cents, or 0.61%, to $51.73.
Increased U.S. drilling activity also weighed on the outlook for supply.
Trading was light with many markets in Asia and Europe closed for the Labor Day holiday.
But oil remained underpinned by hopes for an extension of an output cut deal by major producers.
OPEC and non-OPEC producers have agreed to cut output by 1.8 million barrels a day in the first half.
Iran said over the weekend it would back an extension.
Baker Hughes weekly data Friday showed a rise of nine in the U.S. rig count to 697.
That was the highest number since April 2015.
Higher U.S. output undermines the impact of the output cuts.