The city's beaches remained open after clean-up crews removed the tar balls from shore, authorities said. Even so, the sight is a worry for a state with an annual tourism industry worth US$60 billion.

The largest spill in US history threatens the coastal economies of four states including hard-hit Louisiana. It has also severely dented the British energy giant's finances and reputation and tarnished President Barack Obama's popularity.

The White House criticized BP CEO Tony Hayward for taking time off from dealing with the leak's consequences to watch a yacht race on Saturday off the south coast of Britain. BP said he was taking some much needed downtime.

To minimize the leak's environmental impact, BP is capturing as much as 24,000 barrels (1.008 million gallons/3.81 million liters) a day of crude using two containment systems but that is a fraction of the 35,000-60,000 barrels the US Coast Guard says is pouring from the well.

Under pressure from the White House, BP has set up a US$20 billion damages fund but that figure could be increased if it proves insufficient, said Kenneth Feinberg, the fund's federal administrator.

So far, Louisiana's wetlands and its fishing industry have suffered the worst damage from the spill and downcast fishermen say times are harder than in the aftermath of Hurricane Katrina, which battered the Gulf Coast in 2005.