UNDATED (AP) - The U.S. Gulf Coast is mobilizing to prepare for the approach of Gustav.

Gustav diminished to a tropical storm over Haiti but was still dumping heavy rains as it moved west-northwest at 5 miles per hour.

Forecasters say it could regain hurricane strength soon.

The National Hurricane Center says Gustav is raising concern particularly because there are few surrounding wind currents capable of shearing off the top of the storm and diminishing its power. It says that, "combined with the deep warm waters, rapid intensification could occur in a couple of days."

Royal Dutch Shell began evacuating some 300 workers from offshore rigs, and other companies pulled out non-essential personnel. Any damage to the oil infrastructure or Gulf Coast refineries could send U.S. pump prices spiking, possibly before the busy Labor Day weekend.

Friday is the anniversary of Hurricane Katrina's strike on Louisiana and Mississippi, and Gustav's tentative track raised the possibility of a Labor Day landfall there. But the average error in five-day forecasts is about 310 miles in either direction, meaning the likeliest targets could be anywhere from south Texas to the Florida panhandle.

(Copyright 2008 by The Associated Press. All Rights Reserved.)