Tropical Storm Isaac, back over warm ocean waters, lashed Cuba with winds and rain as it swept toward the Florida Keys, where it was expected to strike at or near hurricane strength on Sunday.
The storm left six dead in Haiti, still recovering from a 2010 earthquake, and at least three missing in the Dominican Republic after battering their shared island of Hispaniola on Saturday.
No deaths or injuries had been reported in Cuba, which got off lightly when the storm crossed its eastern flank instead of raking up the length of the island as originally predicted, but it still sustained damage.
Isaac was expected to strengthen to a Category 2 hurricane, with maximum sustained winds of 105 miles per hour (169 kph), as it crosses the Gulf of Mexico before making landfall at midweek on the US Gulf Coast, somewhere between Florida and Louisiana, the U.S. National Hurricane Center said.
At 8am EDT (1200 GMT) Sunday, Isaac was about 135 miles (220 km) east-southeast of Key West and packing top sustained winds of 65 miles (100 km) an hour, according to the Miami-based NHC.
The storm's driving winds and heavy rains were already being felt intermittently across south Florida and it was expected to be at or near hurricane force when it swept across the Florida Keys by Sunday evening, the NHC said in an advisory.
A storm becomes a hurricane when sustained winds reach a minimum of 74 miles per hour (119 kph).
Energy producers in the Gulf of Mexico were shutting down production and the U.S. Republican Party said it would recess its national convention in Tampa, Florida for a day out of safety concerns as the storm bore down on the state.
The storm could force a short-term shut-down of 43 percent of U.S. offshore oil capacity and 38 percent of its natural gas output, according to forecasters at Weather Insight, an arm of Thomson Reuters.
Republicans, who will formally nominate former Massachusetts Governor Mitt Romney as their presidential candidate for the November election, will convene their four-day meeting on Monday as scheduled, then recess until Tuesday.
Tampa, located on Florida's west coast, faces a threat of from both winds and heavy rains from Isaac, according to NHC meteorologist David Zelinsky.
"For the Tampa area, storm surge values could be three to five feet above ground," Zelinsky said, referring to the threat of storm-driven inundations of the city from Tampa Bay.
In its latest advisory, the NHC said Isaac was churning west-northwest at 20 miles (31 km) per hour. The storm was officially expected to make landfall anywhere between the Florida Panhandle and eastern Louisiana early on Wednesday as a Category 2 hurricane.
CRASHING WAVES, FLOODING
In Cuba, Baracoa, the island's easternmost city, appeared to get the worst of the storm, which sent 13-foot (4-metre) waves crashing over the seawall and into the streets. Cuban TV reports said more than a thousand people had to be evacuated and 50 buildings were damaged.
"The force of the waves has destroyed the farmer's market for small businesses, also the children's area of a park and various homes," said Baracoa resident Olider Aguilera by telephone. "But I can tell you that the people are not afraid. They're accustomed to meteorological phenomena stronger than this," he told Reuters.
In Haiti, Isaac added to the misery of more than 350,000 survivors of the 2010 earthquake still living in flimsy resettlement camps as water gushed into tents and corrugated plastic shacks ripped apart by the wind.
Authorities said six people were known dead, including a 10-year-old girl killed when a wall fell on her and a woman crushed to death by a falling tree.
Many main roads were blocked or impassable and 14,000 people had been evacuated to shelters, authorities said.
In the Dominican Republic, officials said three people were missing, including the mayor of a town near Santo Domingo swept away as he tried to save another person from a flooded river.
Officials said 764 homes had been damaged by the storm and more than 9,600 people evacuated from storm-struck areas.