Millions of people along the U.S. East Coast are scrambling to prepare for a powerful hurricane that authorities fear will cause widespread flooding and power outages.

The governors of seven states — stretching from North Carolina to Connecticut — have declared states of emergency to free up resources ahead of Hurricane Irene, which is expected to make landfall in North Carolina on Saturday.

President Barack Obama also declared a state of emergency for North Carolina and will make a statement about the hurricane Friday .

Homeland Security Secretary Janet Napolitano said Friday that federal authorities are taking the storm very seriously. Napolitano said the president has directed agencies to ensure all the needed resources are available. She said she has been in touch with mayors, governors and first responders in states in the storm's path.

The National Hurricane Center says Irene has slightly weakened, with maximum sustained winds of 175 kilometers an hour, but it remains a dangerous Category Two storm on a five-point scale of storm intensity. Forecasters expect it to strengthen as it nears North Carolina.

In the U.S., hurricane watches and warnings have been issued for much of the East Coast, and authorities in some areas have already evacuated residents and tourists. In New York City, the mayor ordered hospitals and nursing homes in low-lying areas to evacuate.

In Washington, the threat of Hurricane Irene led organizers to postpone Sunday's dedication of a memorial to civil rights leader Martin Luther King, Jr.

The Federal Emergency Management Agency says Irene will have an effect well inland, both from winds and flooding.

The National Hurricane Center says the storm is expected to produce rainfall accumulations between 15 and 25 centimeters. Some parts of the U.S. mid-Atlantic and New England regions are already saturated from recent heavy rains.

Irene, the first hurricane to seriously threaten the United States in three years, killed at least one person in Puerto Rico and two in the Dominican Republic. It also destroyed homes in The Bahamas.