US weather authorities warned that Ernesto could regain hurricane strength with a punch to Florida equal to last year's devastating Hurrican Katrina.

Cuban authorities said they started evacuating tens of thousands of people from areas threatened by the storm.

In Florida, where Ernesto was expected to make landfall later in the week, Governor Jeb Bush, a brother of the US president, ordered a state of emergency, saying the southeastern state "may be threatened by a major disaster."

Authorities ordered all visitors and non-residents in the Florida Keys to head to safety.

A chain of islands connected to the mainland by a series of bridges and a single road, the Florida Keys are a major tourist destination.

The storm's projected track indicates Ernesto would cross Cuba, sweep over the Keys and enter the Gulf of Mexico exactly one year after Hurricane Katrina wrought devastation along the US coast.

Ernesto became this year's first hurricane in the Atlantic season on Sunday morning, but was downgraded to a tropical storm later in the day, when the Miami-based National Hurricane Center said its maximum sustained winds had dropped to 95 kilometers (60 miles) per hour.

Forecasters said it would likely regain hurricane status before it slams into eastern Cuba on Monday morning, and could strenghten further over the Gulf of Mexico.

The storm dumped torrential rains on Haiti as it neared the Caribbean country's southwestern tip, prompting authorities to evacuate people living in fragile homes along threatened areas, and request assistance from UN troops deployed in the troubled nation.

Telephone lines were down in parts of Haiti and domestic flights were suspended.

Ernesto could make landfall in western Florida on Thursday as a dangerous category-three hurricane, packing winds of up to 209 kilometers (130 miles) per hour, the NHC said.

The center's five-day forecasts suggest Ernesto would spare New Orleans and other areas that suffered the brunt of Katrina. But with memories of last year's devastation still fresh, US authorities were closely monitoring the storm's progress.

Hurricane Katrina, also a category-three hurricane, struck the US Gulf Coast on August 29, 2005, killing 1,500 people in Louisiana and Mississippi and leaving hundreds of thousands homeless.

US authorities were keeping in close contact with the hurricane center to ensure emergency officials are ready when the storm hits land.

Authorities urged residents of southern Florida to finalize "disaster plans" and store up on key supplies in readiness for the storm.

Forecasters said people in Mexico's Yucatan peninsula should also keep a close eye on the storm's progress in case it deviates from its projected track.

The center-track of the NHC's projections indicates the hurricane could enter the Gulf of Mexico after churning over the Florida Keys late Tuesday or early Wednesday. After landfall, it could cross Florida and head back to the Atlantic Ocean on Friday.

NASA officials were considering rolling back the space shuttle Atlantis to its hangar to protect it from the storm, a move that would delay by more than a week the scheduled liftoff from the Kennedy Space Center on Florida's east coast.

Forecasters do not rule out a deviation from the anticipated track, and projections show it is also possible the hurricane could make landfall within an area of southeastern Florida that includes Miami.

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