With the known death toll from America’s tornadoes now around 350, President Barack Obama has described the devastation as “heartbreaking”.
His comments came as he visited Tuscaloosa, Alabama, which took the brunt of days of twisters and storms.
The damage could top three billion euros.
“We can’t bring those who have been lost back. They’re alongside God at this point,” he said.
“We can help maybe a little bit with the families dealing with the grief of having a loved one lost, but the property damage, which is obviously extensive, that’s something that we can do something about.”
This is now the US’s deadliest natural catastrophe since Hurricane Katrina in 2005.
The tornadoes mauled seven southern states, recording wind speeds in excess of 200 kilometres an hour.