Haiti has issued a red alert and evacuated families from tiny outlying islands as Hurricane Matthew, the strongest storm to cross the Caribbean in years, shifted its route toward the impoverished country.
Matthew is expected to make landfall in Haiti on Monday (local time) as a major storm bringing 240 km/h winds and extreme rain to the southern coast, simultaneously lashing Jamaica.
It will move on to Cuba early on Tuesday, the US National Hurricane Center said.
With tropical storm conditions expected to reach Haiti on Sunday night, the prime minister's office issued the alert warning for landslides, high waves and floods.
It evacuated residents by boat from small, exposed sandy islands in the south as a precaution on Saturday.
"We have already started evacuations," Haitian Interior Ministry spokesman Albert Moulion said. "The national center of emergency operations has been activated."
On Sunday, boats were prohibited from going to sea.
The slow-moving storm is forecast to dump as much as 101cm of rain in Haiti and up to 64 cm in Jamaica, the Miami-based hurricane centre said.
Matthew was about 545 km southeast of Port-Au-Prince on Sunday morning and the US National Hurricane Center ranked it at Category 4 of the five-step Saffir-Simpson scale of hurricane intensity.
Earlier it had been ranked at the top Category 5.
Cuban President Raul Castro has warned that Hurricane Matthew was twice as powerful as Hurricane Sandy, which devastated Cuba's colonial second city, Santiago de Cuba, in 2012 while the United States prepared to airlift navy families from nearby Guantanamo.
A few miles east, the United States prepared to airlift some 700 spouses and children to Florida from its Guantanamo Bay naval base to wait out the most powerful cyclone to form over the Atlantic since Hurricane Felix in 2007.
Cuba began evacuating residents along its southern coast in the east of the country and plans to gradually move tourists to safer ground in the next 24 to 36 hours, state-run media said.