Isaac could be the first significant storm to hit Haiti since the devastating earthquake. Tropical Storm Emily threatened in 2011, but it weakened before hitting western Haiti.
The forecast map shows Isaac crossing the nation as a tropical storm with winds under 74 mph.
The agency has met with the government in previous summers to discuss contingency plans for major storms, and pre-positioned relief items are available, she said.
Isaac's path remains uncertain, but some computer models show the storm slicing its way up Florida's peninsula. Others send it farther west, into the Gulf of Mexico.
Officials are taking the threat seriously.
"Obviously, we hope Isaac doesn't hit Florida, but we must take every precaution," said Scott, the Florida governor.
While the convention will have the final say on any changes to the planned event, the organizers are working with state and local officials to ensure everyone has the same information, the governor said.
But Tampa is not the only part of Florida that could be hit, and Scott urged Floridians to be prepared.
"What everyone needs to do is to starting tracking it, watch the weather, heed any warnings, get ready, get 72 hours' worth of supplies," he said.
Tampa Mayor Bob Buckhorn said his city is prepared for the 50,000 people headed to there for the Republican National Convention, which starts Monday.
"We have contingency plan after contingency plan," Buckhorn said. "We are ready in the event that it happens. I don't think it's going to be a factor in this particular convention. But we are prepared in the event that it is."
Scott said that any police officers who were going to Tampa will still go, and the Florida National Guard will stand ready to back up authorities around the state.
He said he spoke with Republican candidate Mitt Romney and assured him the state would be ready for the convention.
"We're a hospitality state that knows how to deal with hurricanes," he said.
Possibly complicating matters, the convention site -- The Tampa Bay Times Forum -- is a mandatory evacuation zone once storms reach 96 mph, a Category 2 hurricane, according to the Hillsborough County Hurricane Guide. The current forecast doesn't have Isaac reaching that status.
At the Guantanamo Bay base, officials canceled the pretrial arguments scheduled to get under way in the trial of Khalid Sheikh Mohammed and four others.
Mohammed, who has been held since 2006, is facing charges related to the 9/11 attacks.
Pentagon officials said all court events at Guantanamo were canceled because of the potential hurricane. All detainees have been moved to buildings that can withstand such a storm, and those who flew in for the hearing went back home.
Officials in the Dominican Republic issued a hurricane warning along the nation's southern coast. The nation's center of emergency operations put 18 provinces under red alert as the storm advances.