CHILMARK, Massachusetts — President Barack Obama urged Americans to take immediate precautions as the "extremely dangerous" Hurricane Irene bore down on the US east coast and told them to heed evacuation orders.

"I cannot stress this highly enough. If you are in the projected path of this hurricane, you have to take precautions now. Don't wait. Don't delay. We all hope for the best, but we have to be prepared for the worst."

"If you are given an evacuation order, please follow it," Obama said outside his vacation rental property on Martha's Vineyard, Massachusetts.

"All of us have to take this storm seriously. You need to listen to your state and local officials. All indications point to this being a historic hurricane."

Obama said that federal emergency management officials had been mobilized for days, deploying teams to threatened areas and stockpiling millions of liters of water and medical supplies and meals.

Irene, a category two hurricane, is forecast to make landfall Saturday in North Carolina, where residents were fleeing normally bustling beach communities and could score a direct hit on New York City.