Obama Warns Hurricane Could Be 'Historic'

US President Barack Obama is cutting short his holiday by a night to prepare for the category two storm Hurricane Irene barrelling up the US east coast.

He announced the decision after telling reporters he believes the hurricane could be "extremely dangerous and costly".

"All indications point to this being a historic hurricane," the president in a hastily convened press conference at the farm where he has been staying with his family off the Boston coast.

He will leave his wife and daughters to complete their holiday but return himself to the White House. Advisers say he believes it is the prudent course of action.

Looking earnest, the president urged residents of the eastern US to "take precautions now" ahead of the storm and obey any evacuation orders.

"I cannot stress this highly enough. If you are in the projected path of this hurricane, you have to take precautions now," Mr Obama said. "Don't wait, don't delay."

States of emergency have been declared in seven states and evacuation orders in a number of coastal areas.

New Jersey and North Carolina have announced mandatory evacuations and New York has now followed suit.

Mayor Michael Bloomberg has ordered a mandatory evacuation of people living in low-lying areas of the city.

He previously authorised the evacuation of hospitals and other at-risk institutions in parts of the city.

Bridges have also been ordered to shut down if winds exceed 60 miles-an-hour and the subways will start a system-wide shutdown at noon local time on Saturday.

Winds topping 100 miles-an-hour have already brought chaos to the Caribbean.

US authorities are worried about high winds but also heavy rainfall bringing flashfloods.

From the Carolinas to Cape Cod, 55 million people are in the storm's potential path in one of the most densely populated parts of the United States.

Barack Obama's holiday has been plagued by huge news stories, distracting him from day one.

Turmoil on world markets, an earthquake, a momentous revolution and now a hurricane have guaranteed constant distractions for the president as he tried to recover from the summer's draining political battles in Washington.

With Irene heading straight for some of America's biggest cities and built up areas, he will not be expecting a quiet weekend.