In Galveston, shocked and bewildered residents staggered through the streets as food and water grew scarce. There was little sign of any federal relief efforts.

Residents carry boxes of food away from a point of distribution set up by the Federal Emergency Management Agency after power was knocked out by Hurricane Ike in Pasadena, Texas September 15, 2008. [Agencies]

"FEMA ain't been by, nobody," said disabled retiree Vivian Matthews, who was stranded at her flooded apartment for two days. "They don't give a damn if we live or die."

Four deaths were reported by officials in Galveston, scene of the worst US weather disaster when a hurricane killed more than 8,000 people in 1900. One person was killed in the Houston suburb of Pasadena, the mayor said.

Bush said Texas residents are "very frustrated" by the slow pace of recovery but "my message will be that we hear you and we'll work as hard and fast as we can to help you get your lives back up to normal."

Power outages were the main obstacle to recovery and authorities have warned that some people could be without for days. Electricity is the lifeblood of Gulf Coast refineries that process about a quarter of the country's fuel.

CenterPoint Energy reported it had restored power to 500,000 customers but about 1.6 million remained in the dark, including big Houston-based corporations.

US crude oil futures shrugged off supply concerns and were almost $2 lower at $93.74 a barrel as the Asian trading day began.

Ike caused minimal damage to oil refineries along the Gulf Coast. Companies are preparing to restart operations at the 14 refineries in Texas and Louisiana that remained shut due to Ike, the Energy Department said.

Houston, home to a booming economy thanks to energy demand, was still under a dusk-to-dawn curfew due to lack of power.

Houston's two main airports resumed partial operations. But with debris still littering its streets and windows blown out of office buildings, it could be weeks before the city of more than 2 million people returns to business as usual.