By Stephen Gibbs
BBC correspondent in Havana
Hurricane Ivan is expected to hit Cuba on Sunday evening, by which time some forecasts predict that it will have regained its category five strength.
Ivan could be the worst storm to hit Cuba in 80 years
That would make it the most powerful hurricane to hit the island since 1924.
Cuba is preparing to move hundreds of thousands of people away from the danger zone.
The current forecast is that on Sunday evening it will cross the island on a path that takes it just east of the capital Havana.
The area is prime sugar cane land and home to some of Cuba's most popular tourist destinations.
There are fears that if Ivan's path veers just slightly to the west it will make a direct hit on Havana, home to two million people and where many buildings are already crumbling after years of neglect.
Cuba is only just recovering from last month's Hurricane Charley, which killed four people and left thousands without electricity or running water for weeks.
State media has been warning people that Ivan is likely to cause far more damage.
Cuba does have a long, successful experience in moving hundreds of thousands of people out of the way of hurricanes.
Civil defence officials do not give people the option to stay.
The Cuban President Fidel Castro has said that he expects the Cuban people's revolutionary spirit will see them through this dangerous time.