Hurricane Earl is expected to skim the eastern US coast as it blows in from the Caribbean [NOAA/GALLO/GETTY]

US authorities have issued warnings of catastrophic damage from Hurricane Earl as it churned across the Caribbean past Puerto Rico and headed towards the eastern coast.

Earl, packing winds of up to 215 kilometres an hour, was upgraded to a category four storm on Monday, with forecasters saying it may skim the coastal area later this week.

On the 5-point Saffir-Simpson scale used by the US National Hurricane Center, a category four storm carries a warning that "catastrophic damage will occur" with a high risk of structural damage.

"There is a very high risk of injury or death to people, livestock, and pets due to flying and falling debris," the centre explained on its website.

The centre warned earlier that the strong winds could further trigger "large and dangerous battering waves" of [up to 1.5 metres] in Puerto Rico, while the storm could dump up to 30 centimetres of rain in high areas".

"These rains could cause life-threatening flash floods and mudslides," it added.

Destructive path

Earl churned west-northwest at 24 kilometres an hour, dumping heavy rains and whipping up massive waves as it continued its arc past the Lesser Antilles.

It was however not projected to make landfall immediately, as earlier hurricane warnings for Puerto Rico, and the US and British Virgin Islands were downgraded.

The eye of the storm passed over the French islands of Saint Martin and Saint Barthelemy early on Monday, bringing down trees, blocking roads and damaging power lines.

The French supplier EDF said some 3,500 people were left without power on the two islands, and were planning to send in reinforcements from Martinique to repair downed lines.

Emergency officials in Guadeloupe, where some 4,000 people had no electricity, said winds of up to 170 kilometres an hour were registered in Saint Barthelemy.

Marie-Luce Penchard, the French Overseas Territories minister, told AFP there were no reported loss of life.

She said she planned to travel to the two islands on Tuesday to assess the damage, but said a desalination plant had been hit and water supplies had been disrupted.