By Christopher Johnson
Global benchmark Brent crude oil was down 50 cents a barrel at $71.96 by 0830 GMT. U.S. light crude was 55 cents lower at $66.49.
"Sentiment is sandwiched between a darkening global economic outlook and looming Iranian supply shortages," said Stephen Brennock, analyst at London brokerage PVM Oil Associates.
U.S. crude stocks rose by 3.7 million barrels in the week to Aug. 10, to 410.8 million barrels, private industry group the American Petroleum Institute (API) said on Tuesday. Crude stocks at the Cushing, Oklahoma, delivery hub rose by 1.6 million barrels, the API said.
Official U.S. oil inventory data was due to be published later on Wednesday by the Energy Information Administration.
Investors are concerned by the health of the world economy at a time of escalating trade disputes between the United States and its major trading partners.
The OECD's composite leading indicator, which covers the western advanced economies plus China, India, Russia, Brazil, Indonesia and South Africa, peaked in January but has since fallen and slipped below trend in May and June.
World trade volume growth also peaked in January at almost 5.7 percent year-on-year, but nearly halved to less than 3 percent by May, according to the Netherlands Bureau for Economic Policy Analysis.
The United States and China have been locked in a tit-for-tat trade spat for a few months, gradually adding tariffs to each others' products in a dispute that threatens to curb economic activity in both countries.
Chinese oil importers now appear to be shying away from buying U.S. crude oil as they fear Beijing may decide to add the commodity to its tariff list.
Not a single tanker has loaded crude oil from the United States bound for China since the start of August, Thomson Reuters Eikon ship tracking data showed, compared with about 300,000 barrels per day (bpd) in June and July.
Meanwhile, investors are watching the impact of U.S. sanctions on Tehran, which analysts say could remove as much as 1 million bpd of Iranian crude from the market by next year.
BMI Research said oil markets would "struggle for direction, as uncertainty around both the impact on supply from the Iranian sanctions and escalating trade tensions between the U.S. and China persists".
(Reporting by Christopher Johnson in LONDON and Henning Gloystein in SINGAPORE; Editing by Alexandra Hudson and Emelia Sithole-Matarise)
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)