Urging everyone in Hurricane Irene's path to prepare, President Barack Obama decided to cut his vacation short Friday and return to the White House for a storm he described as potentially historic.

White House spokesman Josh Earnest said the president would leave Martha's Vineyard a day early, on Friday evening, because it would be prudent to be in Washington as Irene strikes the Eastern Seaboard.

Earnest said the president told staff of his decision shortly after urging the millions of Americans in the path of the hurricane to heed instructions from state and local officials, especially if directed to evacuate.

"Don't wait, don't delay," Obama said. The storm was set to rake the coastline from North Carolina to New England over the weekend.

The president, speaking from his vacation rental, said the federal government is "bringing all federal resources to bear" in response.

"I cannot stress this highly enough, if you are in the projected path of this hurricane you have to take precautions now," the president said.

Illustrating government preparations, Earnest said that the administration conducted a national exercise to test emergency preparedness in 2009. He said the exercise included a simulated hurricane that struck New York city. He said the president participated in that exercise.

Though Martha's Vineyard is in Irene's path, Earnest said that Obama's decision to return to Washington Friday was not made out of worry about his personal safety. Earnest said it was uncertain whether first lady Michelle Obama and the couple's two daughters, Sasha and Malia, would join the president or return to the capital Saturday as originally planned.

Obama said he had been briefed on Irene's status Friday morning by top federal officials. He said he also talked to governors of states and mayors of communities in the expected hurricane path, including mayors Michael Bloomberg of New York and Michael Nutter of Philadelphia.

Warnings were in effect from North Carolina to New Jersey.

As the president spoke, rains from Irene's outer bands began hitting the Carolinas, along with 6- to 9-foot waves. On Martha's Vineyard, though, Obama stood in the shade of a poplar tree outside a gray-shingled cottage. Otherwise it was bright sunshine, not a cloud in the sky.

Obama has been in Martha's Vineyard since Aug. 18.

The president, in his remarks Friday morning, cited two government web sites, one in English and one in Spanish, that provide advice on how to prepare for emergencies _ http://www.ready.gov and http://www.listo.gov.

He said the Federal Emergency Management Agency has been deploying teams up and down the East Coast along Irene's projected path. The agency has millions of liters of water, millions of meals and tens of thousands of cots and blankets positioned along the Eastern Seaboard, he said.

The American Red Cross has been preparing shelters in North Carolina and other states, he said.

He cautioned that it would take time for first responders to begin rescue operations and get resources to people in need.

"So the more you can do to be prepared now, making a plan, make a supply kit , know your evacuation route, follow instructions of your local officials, the quicker we can focus our resources after the storm on those who need help the most," he said.

"All indications point to this being a historic hurricane."

Two years ago, Obama's first vacation on Martha's Vineyard as president was delayed by Hurricane Bill.