Ike is huge, taking up nearly 40% of the Gulf of Mexico. The National Hurricane Center said tropical storm-force winds of at least 39 mph extended across more than 510 miles.
Ike and last week's Hurricane Gustav have helped to stanch a sharp downturn in oil prices. Concerns over slowing economic growth on a global scale and a strengthening U.S. dollar have led funds to liquidate their commodities holdings, pushing crude prices down about 30% from their record $147.27 set on July 11.
U.S. fuel demand in June was down 5.6% from the same period a year ago, according to a recent report from the Energy Department, so many market watchers are expecting oil prices to resume their tumble.
"With demand being down as much as it is, the market, some argue, is a bit oversupplied," said Stephen Maloney, a senior consultant in energy risk management at Towers Perrin. "When you ask, how does Ike affect things? Its impacts are going to be in the context of lower demand for products than a year ago."
Associated Press writers Alex Kennedy in Singapore and Louise Watt in London contributed to this report.