US officials have admitted that it is “inevitable” that oil from an uncontrolled leak in the Gulf of Mexico will hit the country’s coastline, threatening an environmental and economic catastrophe.
President Obama is due to visit the region later as efforts to control the spill gather pace.
The oil gushing unchecked from a ruptured deepwater well off the coast of Louisiana is flowing north, pushed by shifting winds.
The coastline from Louisiana to Florida is under threat from the slick, which is thought to have tripled in size in 24 hours.
As many as 5,000 barrels of oil a day are pumping into the sea after the British Petroleum-operated Deepwater Horizon rig exploded and sank.
Wetlands off the Louisiana coast sustain hundreds of wildlife species, as well as major seafood and fishing industries and it is feared the slick could cause enormous damage.