Tens of thousands of people were told to evacuate their homes along some 800 kilometers (500 miles) of US coastline as the powerful storm threatened western Florida, Alabama, Mississippi and Louisiana.

The ferocious storm was expected to land early Thursday along the northern US Gulf Coast, somewhere between New Orleans, Louisiana, and Pensacola, Florida, according to the Miami-based National Hurricane Center.

Because Ivan's powerful winds reach 410 kilometers (260 miles) from the center of the hurricane, the landfall would affect a large swath of land.

If the storm veers of its predicted track, it could also hit parts of Florida, a southeastern US state still mopping up from the ravages wrought by hurricanes Charley and Frances over the past month.

At 0001 GMT, Ivan's center was about 525 kilometers (325 miles) south-southeast of the Mississippi river.

It lost some strength and was downgraded a notch after hitting the western tip of Cuba Monday, but was still packing ferocious winds of 225 kilometers per hour (140 mph), and could regain category five strength, forecasters said.

As the mayor of low-lying New Orleans urged residents to seek shelter on higher ground, officials recalled that the far less powerful Hurricane Betsy had killed 110 people and left the city under more than two meters (seven feet) of water in 1965.

Schools shut down and residents along the threatened areas boarded up their homes and bought emergency supplies, while military bases deployed personnel, planes and ships to safety.

The port of New Orleans was closed through at least Wednesday, said Cynthia Swain, director of safety and security for the port.

"Depending on what the storm does will determine what we do on Thursday," she said.

Florida, Louisiana and Alabama were under a state of emergency and Mississippi joined them in ordering massive evacuations as Ivan roared toward the US coast after wreaking havoc across the Caribbean, from Grenada to Cuba.

Interstate 10, the main east-west highway leading away from the threatened areas, was packed bumper-to-bumper with vehicles for more than 300 kilometers (186 miles) toward Tallahassee, the capital of Florida. Only emergency vehicles headed into Ivan's predicted path.

Ivan's latest rampage was in Cuba, where it raged for three hours late Monday after the eye slammed over Cape San Antonio at the island's western tip, 350 kilometers (220 miles) west of Havana.

Hundreds of homes, fishing and farm installations were damaged as roofs were torn off, trees were felled and mudslides cut off some communities.

There were no immediate reports of casualties in Cuba, which had lost five lives to Hurricane Charley last month. Authorities said it was too early to assess damage from the storm, as recovery efforts had just begun.

In the Cayman Islands, which were hit Sunday, dozens of people were missing, and the British territory remained under a state of emergency, officials said. Many homes were uninhabitable due to damage or flooding, and some roads were blocked.

The US State Department urged US nationals to avoid travel to the islands.

The tiny spice island of Grenada was the worst hit by Ivan, with at least 37 people killed last week, and as many as 90 percent of all buildings damaged or destroyed, officials said.

Thousands of the island's 100,000 inhabitants were still living in shelters, they said.

In Jamaica, police put the death toll at 21 after powerful winds and heavy rain from Ivan tore down houses, felled trees and destroyed roads in the nation of 2.7 million.

The hurricane was also blamed for five deaths in Venezuela, four in the Dominican Republic, three in Haiti and one in Tobago.

Aid for the devastated nations started pouring, with the European Commission announcing it was sending 1.5 million euros (1.8 million dollars) and Canada pledging Canada 500,000 Canadian dollars (385,000 US).

Caribbean leaders were to hammer out a regional disaster plan for hurricane-hit Grenada and Jamaica at an emergency meeting Wednesday in Trinidad.

But as the assistance was on its way, weary Caribbean residents cast a wary eye at Tropical Storm Jeanne, which was gaining strength as it headed for the US Virgin Islands and Puerto Rico, and was expected to become a hurricane by Wednesday.

Hurricane warnings were issued for both US territories. Forecasters said Jeanne was expected to pass over St. Croix by early Wednesday on its way to Puerto Rico, bringing rainfall of up to 25 centimeters (10 inches) and storm surges of up to 1.2 meters (four feet) above normal tides.

Storm warnings also were in place for the Dominican Republic, British Virgin Islands and St. Kitts and Nevis.

Mexico, meanwhile heaved a sigh of relief as Ivan spared its Yucatan peninsula, but kept an eye out for Javier, another powerful hurricane in the Pacific Ocean that appeared headed for Baja California.

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