Tens of thousands of people were told to leave their homes for safer ground ahead of Ivan's anticipated US landfall early Thursday morning.
The governors of Florida, Alabama, Mississippi and Louisiana declared a state of emergency, and ordered evacuations of coastal areas and mobile homes.
"This is a serious storm that requires serious action to get people out of the way," said Mississippi Governor Bob Riley.
On Tuesday afternoon, Ivan was located about 640 kilometers (400 miles) south-southeast of the mouth of the Mississippi River, packing winds of 225 kilometers (140 miles) per hour.
Residents along the swath of land that is expected to be battered by the deadly storm boarded up houses and stocked up on essentials, including water and batteries.
Military bases in the area also battened down the hatches and moved personnel, aircraft and ships to safer areas.
The storm was expected to hit land somewhere between New Orleans, Louisiana and Pensacola, Florida, with the most likely track taking it to the Alabama-Mississippi border, the Miami-based National Hurricane Center said.
New Orleans Mayor Ray Nagin called for an evacuation of the low-lying city, as officials pointed out that the weaker Hurricane Betsy had killed 110 people and left the city under more than two meters (seven feet) of water in 1965.
Local radio reported bumper-to-bumper traffic as residents made their way out of the city of 1.5 million which is about three meters (nine feet) below sea level.
Oil companies were flying personnel off their rigs in the Gulf of Mexico.
The storm would be the third hurricane in a month to hit the United States, with Florida still mopping up after being pounded by Charley and Frances.
Ivan killed more than 70 people as it barreled from Grenada across the Caribbean to Cuba, whose western tip was slammed on Monday evening before the hurricane headed into the Gulf of Mexico.
It lost a little steam and was downgraded one notch from the top category five, but forecasters say it could regain strength before landfall.