NEW YORK (Reuters) - Oil prices settled mixed on Tuesday, with New York-based futures down slightly, as market participants awaited the U.S. government's inventory data amid a global oversupply that was pressuring prices.
Industry group American Petroleum Institute (API) said in a preliminary report U.S. crude stockpiles had risen 7 million barrels last week, way above the 3.7 million barrels expected by analysts in a Reuters survey.
The U.S. Energy Information Administration (EIA) will report official inventory data on Wednesday.
"The API numbers set the stage again for tomorrow's EIA report, which is expected to show a fourth straight week of builds," said Chris Jarvis, analyst at Caprock Risk Management in Frederick, Maryland.
Expressing surprise at the API data, Jarvis said he had expected builds due to seasonal maintenance for U.S. refineries "but certainly not these kind of numbers".
Brent futures for December delivery, settled 10 cents up at $48.71 a barrel. It turned negative in post-settlement trade, trading down 5 cents at $48.56 a barrel by 4:55 p.m. EDT (1655 GMT) after the release of the API data.
U.S. crude futures for November, which expired at Tuesday's settlement, finished down 34 cents at $45.55 per barrel.
The December U.S. contract, which will become front month on Wednesday, settled up one cent at $46.29. That was down 37 cents in post-settlement trade.
"The threat of excessive supply is constantly hitting brief rallies, just like what occurred at the end of the U.S. session today," said Richard Hastings, macro strategist at Seaport Global Securities.
While U.S. shale output was not declining much, Iraqi and Libyan production were strong and Iran was attempting to regain market share once nuclear-related sanctions are lifted against Tehran, Hastings said.
Alongside the regular focus on U.S. oil inventories, analysts said the market was also keeping a close eye on the meeting of OPEC and non-OPEC oil market experts in Vienna on Wednesday.
"I believe the general consensus is nothing will be accomplished insofar as a plan to cut production but I think there is just a level of cautiousness in case of a surprise," said Energy Management Institute analyst Dominick Chirichella.
Major oil exporters in the Middle East are pumping around 2 million barrels per day more crude oil than needed at the moment, analysts say, filling inventories around the world.
Additional reporting by Scott Disavino in New York, Christopher Johnson in London, Keith Wallis in Singapore; editing by Marguerita Choy and Diane Craft