Expressing amazement at the destruction around him, US President Barack Obama has surveyed the wreckage left by rampaging tornadoes in several states including Alabama and pledged help to those who survived but lost their homes.
"We're going to make sure you're not forgotten," Mr Obama said as he and first lady Michelle Obama walked the streets of one neighbourhood.
The president said that although nothing could be done for the many who were killed - "they're alongside God at this point" - he assured support for resilient survivors.
The loss of life - at least 329 dead - is the greatest from an outbreak of US tornadoes since April 1974, when the weather service said 315 people were killed by a storm that swept across 13 southern and mid-western states.
The storms did the brunt of their damage in Alabama. More than two-thirds of the victims lived there, and large cities bore the scars of half-mile-wide twisters that rumbled through.
One of the tornadoes to hit Mississippi on Wednesday had winds of 205mph, the National Weather Service said. That storm was a half-mile wide, was on the ground for three miles and killed 14 people.
"What's amazing is when something like this happens folks forget all their petty differences," said the president after spending time talking to Alabama's governor and Tuscaloosa's mayor.
The president said Tuscaloosa would rebuild in a way that would give him a story of pride he would tell across the nation: "When we're confronted by the awesome power of nature and reminded that all we have is each other."
Later, Alabama Governor Robert Bentley said 1,700 people have been injured by the tornadoes that levelled communities across the state.