Tropical Storm Gustav gained strength Thursday with sustained winds of 110 kilometres per hour as it moved away from Cuba and toward Jamaica, the dpa reported.
"On this track the centre of Gustav will move near or over Jamaica today and tonight (Thursday) and near or over the Cayman Islands Friday night," the US National Hurricane Centre (NHC) said.
Jamaican authorities have issued a hurricane warning, and the Miami-based NHC has warned that "Gustav could become a hurricane before moving over Jamaica."
The NHC warned Gustav is expected to produce rainfall accumulations of 15 to 30 centimetres across Jamaica and the Cayman Islands that could produce life-threatening flash floods and mud slides.
Meanwhile, Jamaicans were rushing to stores to buy supplies. Gustav has already left at least 22 dead and 9,000 displaced in addition to causing severe damage to housing and agriculture as it passed through the Dominican Republic and Haiti.
Cuban authorities were reviewing their preparations in the light of the storm's altered course, which diminished chances of it affecting the nation's eastern provinces. But Jose Rubiera of Cuba's Meteorology Institute urged caution, waring that Gustav may still pass through the island's western tip as a hurricane.
Rubiera recommended that the country remain alert, although for the moment there were no plans for additional large scale evacuations.
On Wednesday, more than 50,000 people had been preventively evacuated from their homes in south-eastern Cuba, to anticipate likely heavy rain, coastal flooding and mudslides.
The US state of Louisiana was also bracing for the storm, which could hit as early as next week and three years after Hurricane Katrina devastated New Orleans. Authorities feared Gustav could disrupt oil drilling in the Gulf of Mexico at a time of already high fuel costs.
New Orleans Mayor Ray Nagin said the city has already begun preparing for evacuations and tests of the emergency responses functioned well.