In choppy trade, the market also watched signs of further financial stress in the United States that pushed Lehman Brothers, the venerable Wall Street investment bank, to the brink of collapse. The US government reportedly was racing to find a buyer.
New York's main contract, light sweet crude for delivery in October, rose 31 cents to close at 101.
18 dollars a barrel.
About an hour earlier, the New York contract briefly dipped to 99.
99 dollars, crossing the psychological 100-dollar threshold for the first time since April 1.
In London, Brent North Sea crude for October dipped six cents to settle at 97.58 dollars.
Brent dropped below 100 dollars Tuesday for the first time since April 2.
In a precipitous decline, crude oil prices have shed about 50 dollars from record peaks above 147 dollars, on July 11.
US weather forecasters said that Hurricane Ike's path made it likely the powerful storm will spare the Gulf oil facilities that produce about a quarter of US crude oil.