Energy giant BP made a new attempt to siphon gushing oil from an offshore well as political pressure and public outrage increased over the company's slow progress at stopping environmental disaster.

London-based BP admitted on Saturday that its latest attempt to contain the spill had failed but a top executive expressed optimism that the tricky undersea effort to redirect the flow of oil would be operational overnight.

The latest fix involves guiding undersea robots to insert a small tube into a 53-cm pipe, known as a riser, to funnel the oil to a ship at the surface.

Crude oil is gushing unchecked into the sea from a blown-out offshore well a mile deep on the floor of the Gulf of Mexico, threatening an ecological and economic calamity along the US Gulf Coast.

Officials said that so far the spill has had minimal impact on the shoreline and wildlife, but oil debris and tar has begun to wash up on barrier islands and outlying beaches of Louisiana, Alabama and Mississippi.

Scientists and residents of the Gulf Coast say a far greater concern is the anticipated encroachment of oil into the environmentally fragile bayous and marshes teeming with shrimp, oysters, crabs, fish, birds and other wildlife.

Workers in Louisiana expressed outrage at comments by BP Chief Executive Tony Hayward suggesting that the size of the spill was 'tiny' compared to the size of the Gulf of Mexico.

'I think he's nuts,' said Kenneth Theriot, 56, a shrimp boat owner and captain in the Louisiana town of Chauvin. 'I don't care how big the Gulf is. It's all coming here.'

Shrimpers and fishermen have been idled by commercial fishing closures imposed because of the spill.

Hayward's comments were published in Britain's Guardian newspaper.

BP's initial attempt to insert the tube into the riser ran into trouble when the metal frame that supports the siphon shifted, BP chief operating officer Doug Suttles told reporters in Robert, Louisiana on Saturday.

Suttles said BP hoped to get the siphoning tube inserted late on Saturday and operational overnight.

A BP spokesman did not respond to inquiries late on Saturday about progress on the latest attempt.

The spill began after an April 20 explosion on the Deepwater Horizon rig, which killed 11 workers. It threatens to eclipse the 1989 Exxon Valdez spill off Alaska as the worst U.S. ecological disaster ever.

Oil plumes

A New York Times report on Saturday said scientists had found huge oil plumes in the Gulf, including one as large as 10 miles long, 3 miles wide and 300 feet thick.

It said the discovery provided evidence that the leak could be 'substantially worse' than estimates given previously by the government and BP.

BP is facing growing political pressure to prove it will pay for all of the costs related to the spill.

'The public has a right to a clear understanding of BP's commitment to redress all of the damage that has occurred or that will occur in the future as a result of the oil spill,' Interior Secretary Ken Salazar and Homeland Security Secretary Janet Napolitano said in a letter to Hayward.

Concerns have been raised about current US law that limits to $75 million energy companies' liability for lost business and local tax revenues from oil spills.

Randy Arceneaux, 28, a fisherman and deckhand in the Cajun village of Cocodrie, deep in Lousiana bayou country, said he was despondent about more than his lost income.

'The food that actually goes on my table came from these waters,' Arceneaux told Reuters. 'People are talking about the money they're losing. It's not just the money. It's the food, it's your livelihood. It's what you were taught, it's what you were raised on, and we'd like to pass it on to our kids,' he added.-Reuters