"All neighborhoods and possibly entire coastal communities will be inundated during the period of peak storm tide," the NHC said in a special bulletin released at 0119 GMT ahead of the powerful storm's forecast landfall late Friday or early Saturday.

"Persons not heeding evacuation orders in single family one- or two-story homes will face certain death," it said.

Slender Galveston island -- about three miles (five kilometers) off the Texas coast and whose city of Galveston has more than 50,000 residents -- could be flooded by a storm surge as high as 22 feet (6.5 meters).

"Life-threatening inundation likely!" blared the warning from the Miami-based NHC, which said that many residences on the immediate coast "will be destroyed," with widespread personal property damage likely elsewhere.

"Entire flood-prone coastal communities will be cut off. Water levels may exceed nine feet (three meters) for more than a mile inland," it said.

"Damage from beach erosion could take years to repair."

Ike, which left more than 100 people dead in its rampage through the Caribbean, was expected to barrel into the Texas coast as a major hurricane packing winds in excess of 120 miles (190 kilometers) per hour.

A mandatory evacuation order was already in effect earlier Thursday, when some residents in Galveston said they were resisting the order to get out.

"There's more people here than I would have thought," said Alicia Cahill, a public information officer for Galveston.

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