Crude futures slipped in Asian trade on Tuesday as investors took profits after prices climbed more than 3 percent in the previous session.
The dollar was also weighing on oil prices after rising against a basket of currencies, suggesting markets were judging Democrat Hillary Clinton as the winner in the first U.S. presidential debate with Republican candidate Donald Trump.
A stronger greenback makes commodities like crude that trade on a dollar basis more expensive for consumers that pay in other currencies.
Expectations of a build in U.S. crude stockpiles last week, according to a Reuters poll, also pressured prices amid concerns of a global oversupply.
Major oil producers are gathering in Algeria for a three-day meeting that could see moves to cut or freeze oil output in an effort to support oil prices.
The Organization of the Petroleum Exporting Countries and other oil producers led by Russia are meeting informally on the sidelines of the International Energy Forum in Algeria from Sept. 26-28.
But markets remained sceptical that producers would reach a deal, said Michael McCarthy, chief market strategist at Sydney's CMC Markets.
"The dominant news for investors is U.S. inventory data unless we see something surprising out of Algiers," he said.
The reversal in oil prices during the Asian time zone on Tuesday meant investors were generally profit-taking, McCarthy said.
Brent crude futures slipped 15 cents to $47.20 a barrel as of 0346 GMT after closing up $1.46, or 3.2 percent in the previous session.
U.S. West Texas Intermediate (WTI) crude fell 6 cents to $45.87 a barrel, after rising $1.45, or 3.3 percent, in the previous session.
U.S. commercial crude oil stocks likely rose by an average of 2.8 million barrels to 507.4 million barrels in the week to Sept. 23, reversing three weeks of unexpected drawdowns, a Reuters poll of seven analysts showed.
That came ahead of weekly inventory reports from industry group the American Petroleum Institute (API) that will be released later on Tuesday, and the U.S. Department of Energy's Energy Information Administration (EIA) that will be published on Wednesday.
OPEC member Iran on Monday downplayed the chances of oil producers clinching an output-restraint deal although several other producers, including the United Arab Emirates and Algeria, hoped measures could be agreed to curb output.
"With the market still unconvinced an agreement will be reached, any signs that OPEC will cap output could see prices surge higher," said ANZ in a market report on Tuesday.
(Reporting by Keith Wallis; Editing by Joseph Radford and Christian Schmollinger)