US President George W. Bush toured parts of flood-ravaged Iowa on Thursday, praising exhausted rescue workers and promising swift aid for relief and to rebuild the storm-battered region.

"Obviously, to the extent that we can help immediately, we want to help, and then plan for recovery," said Bush, who took sharp criticism over Washington's sluggish response to Hurricane Katrina in 2005.

On May 25, tornadoes and record rainfall struck the Midwest and lasted for weeks resulting in severe flooding in ten states, with 24 killed, about 100 injured, and at least 35,000 people evacuated, according to the US government.

"A lot of people aren't getting much sleep these days -- you're exhausted, I understand that," Bush told relief workers. "Our hearts and prayers from around the nation go out to people here. It's a tough time for you."

The head of the US Federal Emergency Management Agency, David Paulison, said authorities sometimes working with the private sector have delivered 3.3 million liters of water, as well as 200,000 ready-to-eat meals.

Relief workers have also brought 146 generators, 50 miles of plastic sheeting, and FEMA was on its way to set up 30 mobile disaster recovery centers, Paulison said aboard Bush's Air Force One airplane.

"That's to help people get registered, so if they can't necessarily travel to where the state's disaster recovery centers are, we can go out to where they are. Another lesson we learned in Katrina," he said.