Oil prices dropped on Wednesday after an industry group reported that U.S. crude inventories rose last week, defying analyst expectations for a significant reduction.
Brent futures were down 31 cents, or 0.4 percent, at $71.85 a barrel by 0240 GMT. They rose 32 cents to $72.16 a barrel on Tuesday, after earlier touching a three-month low, Reuters said.
U.S. West Texas Intermediate crude was down 36 cents, or 0.5 percent, at $67.72. It settled up 2 cents at $68.08 a barrel the session before, coming off a nearly one-month low.
The benchmarks had steadied after big declines on Monday and last week as supply disruptions in Venezuela came to the fore and as analysts had been forecasting a decline of 3.6 million barrels in U.S. inventories for the week through July 13.
But the specter of oversupply quickly returned, with a rise of more than 600,000 barrels in U.S. crude stockpiles, reported by the American Petroleum Institute late on Tuesday.
Official numbers from the U.S. Department of Energy's Energy Information Administration are due at 10:30 a.m. EDT on Wednesday.
On the demand-side, intensifying risks over trade tensions between the United States and China could drag on the global economic outlook, BMI Research said.
"Despite U.S.-China trade tensions, the economic outlook is broadly positive, but a number of headwinds are emerging, not least a stronger dollar, rising inflationary pressures and tightening liquidity," BMI said.
"Slowing trade growth will weigh on physical demand for oil, with the shipping, road and air freight sectors an important pillar of demand globally," BMI said.