"I want people to understand that this is not over. Response and recovery efforts will be an ongoing operation," Obama told reporters on Sunday.
"I do want to underscore that the impacts of this storm will be felt for some time, and the recovery effort will last for weeks or longer," he said in his appearance at the Rose Garden with Secretary of Homeland Security Janet Napolitano.
"Power may be out for days in some areas, and we will support our state and local partners in every way that we can as they work to restore power in those areas," he said.
The death toll in the US from Irene has risen to 18. Obama urged his countrymen in affected areas to continue to listen for the guidance of their state and local officials.
"Before the storm made landfall, the Department of Homeland Security and FEMA worked very closely with our state and local partners, as well as volunteer organizations, to pre-position supplies and teams of first responders along the hurricane's projected track. And the American Red Cross opened shelters in communities across the region," he said.
Napolitano said the US Government will be dealing with the impacts of this storm over the coming days, and she urged all Americans to take prudent steps to stay safe.
"Now, dealing with a storm like this requires a three- phase approach: preparation, response and recovery. Some states and communities are still currently responding, while others are beginning to assess their damages and plan for recovery," she said.