U.S. forecasters say Gustav has returned to hurricane strength as the storm crosses the Caribbean towards the Gulf of Mexico.
Gustav was expected to pass near or over the Cayman Islands later Friday and western Cuba on Saturday. Forecasters say the storm that has already caused at least 72 deaths could produce more than half a meter of rain in some areas.
The Miami-based National Hurricane Center said Gustav had sustained winds of up to 120 kilometers per hour mid-afternoon Friday. The center says the Category one storm is likely to grow into a major hurricane over the warm waters of the Gulf of Mexico.
U.S. authorities in Gulf coast states of Louisiana, Mississippi and Texas are evacuating some residents voluntarily Friday and Saturday. Mandatory evacuations are scheduled for Sunday.
New Orleans residents prepared for the storm as Friday marked the third anniversary of Hurricane Katrina, which killed hundreds and caused more than $100 billion in damage.
U.S. President George Bush has declared that a federal state of emergency in the state of Louisiana, a likely target for Gustav.
The U.S. Department of Energy said Friday that oil installations in the Gulf of Mexico are better protected than they were in 2005. Thousands of workers have been evacuated from the installations. Officials also said they were prepared to provided 4.4 billion barrels a day of oil from strategic reserves to offset any production losses caused by the storm.
Gustav lashed Jamaica with torrential rains and high winds Thursday and Friday. The storm has killed at least 72 people in Jamaica, Haiti and the Dominican Republic.
Meanwhile, Tropical Storm Hanna was passing about 345 kilometers north of the Leeward Islands on Friday morning. It was expected to pass north of the Virgin Islands and Puerto Rico Friday night or Saturday.