WASHINGTON — Seeking to avoid a Hurricane Katrina-like leadership failure, President Obama assured the nation yesterday he was keeping close watch on the Midwest floods and putting the government's full weight behind efforts to prevent disaster.

"Even as we face an economic crisis which demands our constant focus, forces of nature can also intervene in ways that create other crises to which we must respond — and respond urgently," the president said in his weekly radio and Internet address.

"I will continue to monitor the situation carefully," he pledged. "We will do what must be done to help."

Obama also implored residents of North Dakota, South Dakota and Minnesota to be vigilant in reading flood-condition reports and to follow instructions from federal, state and local officials should evacuation be necessary. He repeatedly praised volunteers stockpiling sandbags and building levees, saying "their service isn't just inspirational — it's integral to our response."

In office just two months, Obama and his team no doubt are mindful of the Bush administration's bungled response in August 2005 to Hurricane Katrina, which devastated the Gulf Coast and highlighted the country's racial and economic divisions. George W. Bush's popularity took a beating in Katrina's aftermath, and the hurricane has been held up ever since as a symbol of the federal government's incompetence.

Obama used his weekly address to go to great lengths to describe all that the federal government has been doing as bulging rivers and streams threatened Midwest communities over the past few days. Aides said federal, state and local officials have been coordinating for more than a week.

Over the past few days, Obama signed emergency and disaster declarations for North Dakota and Minnesota, triggering federal support to help state and local officials who already had efforts under way. Yesterday, he indicated that help for South Dakota could come soon, saying his aides were "keeping close watch on the situation" there.