New York's main contract, light sweet crude for June delivery, dipped 26 cents to $99.84 a barrel and Brent North Sea crude for July delivery lost 16c to $112.14 in the afternoon.
Ker Chung Yang, a Singapore-based commodity analyst at Phillip Futures, said the dip was "quite minimal as the market is still underpinned by the fall in crude stockpiles" in the United States.
A decline in crude stockpiles is a sign of stronger demand in the world's biggest oil consuming nation.
The US Department of Energy (DoE) in its weekly report on Wednesday showed American crude stockpiles had failed to rise as expected in the week ending May 13.
Stockpiles steadied last week, bucking forecasts for a rise of 700 000 barrels, according to analysts polled by Dow Jones Newswires.
"This was one key reason why crude oil prices was performing impressively," Ker said.
"Crude oil prices will likely hang around the $100 level for quite some time unless there is a strong impetus to bring it down," Ker told AFP.
Traders closely monitor the DoE report for clues on demand in the world's biggest economy.