Felix, which has maximum winds of near 65 mph (100 kph), skirted the Caribbean island of Grenada overnight.
It has been moving west in the past 12 hours though a strong ridge is due to steer the storm slightly northward in the next few days, the hurricane center said at 11 a.m. EDT.
"We are forecasting it to be a Category 3 hurricane in the northwestern Caribbean Sea by the middle of the week," said forecaster Eric Blake of the National Hurricane Center in Miami.
There were no indications the storm would reach the Gulf of Mexico, home to a third of U.S. domestic crude oil and 15 percent of natural gas production. But long-range forecasts are unreliable, the center said.
Energy markets have watched tropical storms and hurricanes closely since the devastating Atlantic hurricane seasons of 2004 and 2005, when storms like Ivan, Katrina and Rita disrupted supplies.
At 11 a.m., Felix was located 455 miles south southeast of Puerto Rico and was moving west at about 18 mph (30 kph), with winds expected to strengthen in the next 24 hours, the hurricane center said.
Computer models predicted the sixth named storm of the year in the Atlantic basin would head into the Caribbean in the general direction of Mexico and Central America.
"All atmospheric and oceanic parameters support a continued strengthening of the storm. With such a favorable environment ... it is likely that Felix will become a powerful hurricane by the time it reaches the northwestern Caribbean Sea," the hurricane center said.
On its current track, Felix was expected to move away from the southern Windward Islands and pass near the islands of Aruba, Bonaire and Curacao late on Saturday or early Sunday.
Those islands, along with parts of the northern coast of Venezuela, were under tropical storm warnings, alerting residents to expect storm conditions within 24 hours.
The 2007 hurricane season, expected to be a busy one, is approaching its peak. Most storms from August 20 to mid-October, with September 10 marking the top.
The only hurricane of the Atlantic season to date, Dean, turned into a monster Category 5 storm, the highest level on the five-stage Saffir-Simpson scale of hurricane intensity.
Dean hammered Martinique, St. Lucia and other islands in the Lesser Antilles chain, blasted Jamaica and then struck Mexico's Yucatan Peninsula before dissipating over the Mexican mainland.
It killed at least 27 people when it moved across the Caribbean and Mexico in late August.
Last Mod: 01 Eylül 2007, 21:03