Chris Sisco, of the National Hurricane Centre, told Al Jazeera: "Ike is heading towards eastern Cuba in the next 12 hours, bringing high seas and quite a bit of rain.
"It is extremely dangerous. The maximum danger is for eastern Cuba."
More than half a million people left Cuba's northeast coast, officials said. Jose Ramon Machado, the Cuban vice-president, asked people to "carry out the evacuation in an orderly and speedy fashion".
In Havana, the capital, many of the colonial-era buildings in a poor state of repair are vulnerable to high winds. Last week's storm Gustav seriously damaged at least 140,000 properties.
George Bush, the US president, said his country would not be lifting its economic embargo on Cuba, despite the negative impact of the Atlantic hurricane season.
Ike is a category four hurricane on the Saffir-Simpson scale, the strongest being category five.
Ike also has the potential to strike the southern Florida Keys, threatening Louisiana and the rest of the US Gulf Coast, which last week weathered Hurricane Gustav.
Hundreds of people in Haiti have moved to higher ground, leaving the town of Gonaives steeped in flood water. Many are going without food and shelter.
Some residents climbed on top of cars to reach the second floor of their homes, where they had piled up furniture and spread sheets to provide shade, Holly Inurreta, from Catholic Relief Services, said.
|This satellite image shows Ike as it moves towards Cuba
Tropical Storm Hanna left hundreds of people dead and hundreds of thousands of people have been displaced.
Teresa Bo, Al Jazeera's correspondent in Gonaives, said: "This storm has already worsened what already was a critical situation ... and there could be mudslides."
Locals are "blaming the government and the United Nations because they have not eaten anything for days," she said.
Bo said further rain is making rescue operations even more difficult.
Hell on earth
In Gonaives, UN peacekeepers and aid workers are delivering high-energy biscuits and water to storm survivors, many of whom have not eaten since Monday.
"What I saw in this city today is close to hell on earth," Hedi Annabi, a UN envoy, said.
Everton Fox, Al Jazeera's meteorologist said: "Ike is making its way away from The Turks and Caicos islands pretty quickly.
"It is moving at about 25km per hour and will steadily head towards Cuba in a direct hit."
Fox said the storm will hit Cuba "strongly" but is then expected to "slow down significantly and become a category one hurricane by the time it leaves the country.
Due to a huge amount of rainfall in Cuba "there will be landslides, flash flooding and widespread devastation," he predicted.
Dozens of children raised their hands and ran after UN food trucks that rumbled through the damp streets of Gonaives. "Hungry! Hungry!" they yelled.
Food also was brought to hungry inmates at the local jail.
The water in many neighborhoods has receded from about three metres high to about knee deep, but at least 40,000 people remain in emergency shelters.
However, the death toll in Gonaives has been reduced after Ernst Dorfeuille, the police commissioner for the city, told the Associated Press that a news report the previous evening that quoted him as saying 495 bodies had been found in Gonaives following Tropical Storm Hanna was completely wrong.
He said there were 32 confirmed deaths in this city on Haiti's west coast from the storm that hit on Monday.