Hurricane Earl strengthened into a major storm as it lashed the northeast Caribbean islands on a track that could swipe the US East Coast.
But the US National Hurricane Center said it was too early to say which part of the US eastern coast might be affected by Earl, the second major hurricane of the 2010 Atlantic season.
A direct hit could not be ruled out, and Earl was expected to bring drenching rain, dangerous seas and surf and gusting wind to the Atlantic Coast from North Carolina to New England and Canada, said Alex Sosnowski, a senior meteorologist for private forecaster AccuWeather.
"How nasty the weather gets in this region will depend on the exact track of Earl and its proximity to the coast," Sosnowski said in a posting on the AccuWeather website.
If Earl swings farther west than expected, heavy rain could sweep the Interstate 95 corridor from North Carolina to Washington, DC, Philadelphia and New York City, he said.
On its current path, Earl posed no threat to the Gulf of Mexico, where major US oil and gas installations are located.
Hovensa LLC said operations were normal at its 500,000 barrel-per-day refinery on the island of St Croix but that the refinery's harbor and all other ports in the US Virgin Islands had been closed because of Earl.