President Barack Obama has declared a state of emergency in Louisiana, as Tropical Storm Isaac threatens to hit the United States as a category two hurricane.
Isaac is heading for New Orleans - possibly as early as Tuesday night - nearly seven years to the day after Hurricane Katrina devastated the city, the BBC reports.
The Republican Party delayed by a day the start of its national convention in Tampa, Florida.
Isaac has killed at least 24 people in Haiti and the Dominican Republic and the storm wrought significant flooding and damage in the Caribbean.
The National Hurricane Center warns Isaac could reach category two strength, with top winds of 160km/h.
Mr Obama approved Louisiana's request for a federal disaster declaration, making available federal funds for recovery activities such as clearing debris.
The governors of Louisiana, Florida, Mississippi and Alabama have declared emergencies in their states.
The Republican governors of Alabama, Louisiana and Mississippi have cancelled their trips to their party's convention to focus on disaster prevention efforts.
Oil companies have already evacuated offshore oil rigs and closed refineries along the Gulf Coast.
By Monday afternoon, 78% of crude oil production and 48% of natural gas production had been shut down.