“We are going to do everything we can to help these communities rebuild,” Obama told reporters after touring smashed homes and talking with survivors in Tuscaloosa, a university city in Alabama that was wrecked by the tornadoes.
Alabama was the hardest hit of seven southern states that were blasted this week by a swarm of tornadoes and violent storms that flattened whole neighbourhoods. It was the deadliest US natural catastrophe since Hurricane Katrina in 2005.
“I have never seen devastation like this. It is heartbreaking,” said Obama, accompanied by his wife Michelle and Alabama Governor Robert Bentley. “This is something I don’t think anyone has seen before.”
Emergency officials raised the death toll from the tornadoes in Alabama alone to 228. Governor Bentley said 1,700 people were injured.
At least 100 more deaths were reported across Mississippi, Tennessee, Arkansas, Georgia, Virginia and Louisiana.
“We can’t bring those who’ve been lost back. They’re alongside God at this point... but the property damage, which is obviously extensive, that’s something we can do something about,” Obama said.
He was eager to show that federal relief is on its way and that he is not taking the disaster lightly.
His predecessor George W Bush was fiercely criticised for what was viewed as a slow response to Hurricane Katrina.
Flying into Tuscaloosa aboard Air Force One, Obama saw a wide brown scar of devastation several kilometres long and hundreds of yards wide.
Tuscaloosa resident Jack Fagan, 23, said he was glad that Obama saw the damage. “Perhaps federal funds will help us, but I’m sure it will take longer than they say because it always does.”
Recovery could cost billions of dollars and could complicate efforts by affected states to bounce back from recession.
It will also put an added burden on some states grappling with fragile finances.
Tornadoes are a regular feature of life in the US south and midwest, but they are rarely so devastating.