Waves crash on shore near the Cape Hatteras Lighthouse in Buxton, North Carolina, as tropical storm Ophelia lurks off of the US east coast

Three east-coast U.S. states are preparing for Tropical Storm Ophelia, which could regain strength Tuesday before reaching U.S. shores.

The National Hurricane Center says the slow-moving storm could return to hurricane status Tuesday or early Wednesday, as it moves toward land. A hurricane warning has been issued for parts of North and South Carolina.

South Carolina Governor Mark Sanford has issued a voluntary evacuation order for oceanfront and riverfront areas, while the governors of Virginia and North Carolina have both declared a state of emergency in preparation for the storm.

Ophelia is a much weaker storm than Hurricane Katrina, which battered the U.S. Gulf Coast two weeks ago, but officials say it could cause considerable damage because it is moving so slowly.

Ophelia's winds dropped to about 115 kilometers an hour Monday, just below hurricane level (119 kph).