By Aaron Sheldrick
October Brent crude futures dropped 30 cents, or 0.4 percent, to $73.91 a barrel by 0325 GMT, adding to a 1.8 percent loss in the previous session.
U.S. crude futures were down 37 cents, or 0.5 percent, at $68.39 a barrel, having dropped nearly 2 percent on Tuesday.
Brent fell more than 6 percent in July, while U.S. crude futures slumped about 7 percent, the biggest monthly decline for both benchmarks since July 2016.
Data from the American Petroleum Institute (API) showed domestic crude inventories rose by 5.6 million barrels last week. A Reuters poll had forecast a fall of 2.8 million barrels.
Official data from the U.S. Energy Information Administration (EIA) is due later on Wednesday.
"API...showed a big build. So all eyes will be on the EIA data this evening," said Greg McKenna, chief market strategist at AxiTrader.
Signs that a supply disruption in the Bab al-Mandeb Strait in the Red Sea could be resolved also weighed on prices.
Yemen's Houthi group said it was ready to unilaterally halt attacks in the Red Sea to support peace efforts. Saudi Arabia suspended oil shipments through the strait last week after the Houthis attacked two Saudi oil tankers.
A Reuters poll showed that oil prices are likely to hold fairly steady this year and next as increased output from OPEC and the United States meets growing demand led by Asia and helps to offset supply disruptions.
OPEC has pledged to offset the loss of supply from Iran, the group's third-biggest producer.
Looming U.S. sanctions have already started to cut Iranian exports, with buyers from its biggest customers in Asia cutting imports to a seven-month low in June.
(Reporting by Aaron Sheldrick; editing by Richard Pullin)
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)