In a bid to answer recent criticism, President Obama is paying a second visit to Louisiana to supervise the clean-up of the Gulf of Mexico oil spill. He is expected to spend two hours in the area. The spill now ranks as the worst in American history. Here is the BBC's America's editor Mark Mardell.

President Obama has flown over the maze of waterways and green marshlands before his tour of the stricken beaches. He's earlier said that anyone who thinks the federal government hasn't done enough doesn't know the facts, but he admitted they had made three errors - not anticipating a disaster like this could happen, underestimating the size of the leak and not dealing fast enough with what he called the corrupt relationship between government and the oil industry.