Tar balls reach Alabama coast

Concern grew yesterday that the US Gulf coast is facing a whole new level of environmental disaster after the best short-term fix for a massive oil spill ran into serious trouble.

BP's giant containment box lay idle on the seabed as engineers furiously tried to figure out how to stop it clogging with ice crystals, preparing for attempts to resuscitate their vital mission in the next day or so.

The British energy giant, which owns the lion's share of the leaking oil and has accepted responsibility for the clean-up, has tried to banish the notion that the so-called "dome" is a "silver bullet" to end the crisis.

But should efforts fail to make the giant funnel system effective, there is no solid plan B to prevent potentially tens of millions of gallons of crude from causing one of the worst ever environmental catastrophes.

Untold damage is already being done by the 3.5 million gallons estimated to be in the sea so far, but the extent of that harm will rise exponentially if the only solution is a relief well that will take months to drill.

There are also fears that the slick, which covers an area of about 5,200 square kilometres, could be carried around the Florida peninsula if it spreads far enough south to pick up a special current.

"If this gusher continues for several months, it's going to cover up the Gulf coast and it's going to get down into the loop current and that's going to take it down the Florida Keys and up the east coast of Florida," warned Florida senator Bill Nelson.

"You are talking about massive economic loss to our tourism, our beaches, to our fisheries, very possibly disruption of our military testing and training, which is in the Gulf of Mexico," he told CNN's "State of the Union" programme.

The BP-leased Deepwater Horizon rig sank some 50 miles southeast of Venice, Louisiana on April 22, two days after an explosion that killed 11 workers.

The riser pipe that had connected the rig to the wellhead now lies fractured on the seabed a mile below spewing out oil at a rate at some 5,000 barrels, or 210,000 gallons, a day.

Sheen from the leading edge of the slick has surrounded island nature reserves off the coast of Louisiana and tar balls have reached as far as the Alabama coast, threatening tourist beaches further east.

Sealife is being affected in a region that contains vital spawning grounds for fish, shrimp and crabs and is a major migratory stop for many species of rare birds.

The $2.4 billion Louisiana fishing industry has been slapped with a temporary ban in certain areas due to health concerns from potentially polluted fish.