At 2100 GMT, the hurricane's centre was about 480 km south-southeast of Nantucket, Massachusetts, which is near Martha's Vineyard, and about 940 km south-southwest of Halifax, Nova Scotia.

The storm is expected to weaken as it hits the cooler waters of the North Atlantic.

Stormy seas were still washing across the Bahamas and Bermuda. Local officials were warning of extremely dangerous rip tides and surf conditions along the US coast, where many beaches have been closed.

Obama and his family - wife Michelle and daughters Sasha and Malia - are renting Blue Heron Farm, a Martha Vineyard estate owned by a Mississippi businessman who is a registered Republican and a contributor to Obama's rival for the presidency in 2008, Senator John McCain, according to the Vineyard Gazette.

Costs for rental of the 11.5-hectare property, estimated at $35,000-50,000 for the week are to be divided one-third each between the Obamas, his security protection team and the White House entourage, the newspaper reported.

The waterfront property has a swimming pool and a basketball court, offering the president one of his favourite past time of hoops.