ABC News' Tahman Bradley Reports:

As a weakened but still dangerous Tropical Strom Irene pushes up the East Coast, President Obama urged Americans to remain vigilant.

"I want people to understand that this is not over," Obama said in a statement delivered Sunday afternoon in the Rose Garden.

"Though the storm has weakened as it’s moved north, it remains a dangerous storm that continues to produce heavy rains," he added.

The president expressed his condolences to the families of the victims claimed by the deadly weather.  "Our thoughts and prayers are with those who’ve lost loved ones and those whose lives have been affected by the storm.  You need to know that American will be with you in your hour of need."

The federal government remains concerned about the possibility of significant flooding and widespread power outages because of reports that have come in from state and local officials, the president said.  "Many Americans are still a serious risk of power outages and flooding which could get worse in the coming days as rivers swell past their banks."

Obama asked that Americans listen and follow the guidance of state and local governments. He also stressed that even after the storm ends, the clean up could take a while. "I do wanna underscore that the impacts of this storm will be felt for some time, and the recovery effort will last for weeks or longer."

The president pointed out that those Americans who’ve lost power along the East Coast may have to wait longer than they expect for their power to be restored. "Power may be out for days in some areas and will support our state and local partners in every way that we can as they work to restore power in those areas."

Over the weekend, Obama has made the case that the government has done a good job preparing and responding to Irene, hoping to show that his government has learned lessons from the poorly handed emergency responses in the past.   He did so again in his Rose Garden remarks, saying that emergency responders’ good work has saved lives.

"This has been an exemplary effort of how good government, at every level, should be responsive to people’s needs, work to keep them safe, and protect and promote the nation’s  prosperity.

Homeland Security Secretary Janet Napolitano and FEMA Administrator Craig Fugate stood by President Obama during his statement.