The system was moving very little but was expected to head west-southwest, then turn west later today as it passed very close to Jamaica.
Most computer weather models still showed the storm heading in a north-westerly direction, skirting the southern coast of Cuba, then entering the central Gulf of Mexico on Sunday.
While extended hurricane track projections are not always accurate, Gustav's current path could take it through key oil and gas producing areas off the coast of Louisiana or Texas on Monday and Tuesday as a powerful Category 3 storm with winds of about 115 mph.
U.S. oil and gas companies including Shell and BP started evacuating staff from offshore Gulf of Mexico platforms on Wednesday, and more evacuations were expected as long as the current projected storm track holds.
U.S. crude oil prices have gained more than $5 a barrel or 4 percent this week on concerns that Gustav could damage offshore oil platforms or disrupt key U.S. Gulf Coast refining operations.