Evacuation orders have been issued across many areas on the United States’ east coast as Americans faces down what is predicted to be one of the most powerful storms to hit the country in years.

Low-lying parts of New York city as well as coastal areas in Virginia, Delaware and Maryland have all received evacuation orders while US President Barack Obama also issued a state of emergency in North Carolina.

Meanwhile passenger rail operator Amtrak will start canceling trains on its busy Northeast routes tomorrow, while the New York Subway system will also close over the weekend.

More than 50m people live in the potential path of the storm from North Carolina to New England, including residents of Washington DC.

Earlier, President Obama said all the signs pointed to Irene being a ‘historic’ hurricane and urged those living in its path to heed safety warnings.

President Obama has decided to return from his holiday slightly earlier than planned, leaving the island of Martha's Vineyard today rather than tomorrow morning.

Forecasters have predicted Irene will be the most powerful storm to hit the east coast of the United States in years.

Ports, industries, oil refineries and nuclear plants are scrambling to activate emergency plans, while residents stock up on food and water and work to secure homes, vehicles and boats.

Defense Secretary Leon Panetta has also said the military stand ready to aid the response to Hurricane Irene, with some 101,000 National Guard forces available if needed to the affected states.

Meanwhile the US Navy sent the ships of its Second Fleet out of port at Hampton Roads, Virginia, to ride out the expected powerful storm at sea.

Irene has already battered the low-lying Bahamas, southeast of Florida, as a major category 3 storm with winds of up to 153km/h.

Virginia Governor Bob McDonnell urged residents to seek shelter by tonight, before the winds kick up.

'Saturday is going to be a horrendous day for travel. There will be roads and bridges closed,' he said.

Department issues advice to Irish citizens

The Department of Foreign Affairs and Trade has advised Irish citizens travelling to or residing in coastal areas of the eastern US from the Carolinas to New England to exercise caution as Hurricane Irene is due to pass through the area within the next 48 hours.

It says citizens living in the affected areas should monitor local news and weather reports and follow the advice of local authorities.

Visitors should contact their travel agent or tour operator as the deteriorating weather conditions are likely to lead to significant travel disruption, including at major east coast airports, over the coming weekend.

Meanwhile, Aer Lingus has cancelled a number of flights to and from JFK Airport in New York in anticipation of the hurricane.

Six Sunday flights have been halted so far, with the airline saying that as Hurricane Irene moves towards the east coast of the US operations may be further disrupted in New York and Boston.

Aer Lingus said it continued to monitor the situation closely and intending passengers should check the airline's website for updates before leaving for the airport.

The airline said that anyone booked to travel to/from New York or Boston from today (26 August) until Monday 29 August could rebook their travel at no additional charge.