At 5 p.m., the storm was a Category 4 hurricane with sustained winds of 135 mph, about 505 miles northeast of the Leeward Islands, the U.S. National Hurricane Center in Miami reported.

"It is too early to determine what land areas might eventually be affected by Ike," the report said. "This is an extremely dangerous Category 4 hurricane on the Saffir-Simpson hurricane scale."

Hurricane-force winds were extending outward 45 miles from the center, while tropical storm-force winds extend up to 140 miles, the hurricane center said.

"Some weakening is forecast during the next day or so but Ike is expected to remain a powerful hurricane for the next several days," the report said.