Obama promises help to rebuild tornado-hit US South

President Barack Obama flew to the epicenter of one of the United States' worst ever tornado disasters to pledge federal support for recovery after 310 people were killed by destructive twisters.

The president and his family visited the wrecked university city of Tuscaloosa in Alabama, the hardest hit of seven states that were blasted this week by tornadoes and storms that flattened whole neighborhoods. It was the worst US natural catastrophe since Hurricane Katrina in 2005.

In Alabama alone, 210 people lost their lives.

Approaching the airport in Tuscaloosa, Air Force One flew over the tornado strike zone, giving Obama and his family a clear view of a wide brown scar of devastation several miles (kilometers) long and hundreds of yards (meters) wide.

The president is eager to show that federal relief is on its way and that he is not taking the disaster lightly. His predecessor President George W. Bush was fiercely criticized for what was viewed as a slow response to Hurricane Katrina.

White House spokesman Jay Carney said Obama "wants to put a spotlight for the rest of America on the suffering that a storm like this implies for so many families."

Recovery could cost billions of dollars and even with federal disaster aid it could complicate efforts by affected states to bounce back from recession. It will place an added burden on municipalities grappling with fragile finances.