The US government piled pressure on BP Plc today to clean up a "massive environmental mess" in the Gulf of Mexico amid growing anger at the oil giant's failure to contain a five-week-old oil spill.
The company insisted it was doing all it could to try to shut off a blown-out oil well spewing hundreds of thousands of gallons of oil into the Gulf every day. It threatens to become the worst US oil spill in history.
London-based BP, which has now lost about 25 per cent of its market value - almost $50 billion - since the spill began, said it would make another attempt to plug the leak on Wednesday, but gave it only a 60-70 per cent chance of success.
With heavy oil already washing into fragile marshlands and wildlife refuges in Louisiana, the US government is pushing BP to try to contain or seal the leak as soon as possible.
"We will keep our boot on their neck until the job gets done," US interior secretary Ken Salazar told reporters after touring affected areas of the Gulf coast with homeland security secretary Janet Napolitano and a group of US senators.
President Barack Obama has called it an unprecedented environmental disaster for the United States.
Louisiana governor Bobby Jindal said some 113 km of his state's coastline had been affected by the oil spill. He renewed a plea for federal authorities to send more equipment, especially booms, to help stop the oil from making landfall.
More than 1,100 vessels, 24,000 personnel and 2 million feet of boom have been deployed to deal with the spill, the largest such effort in history, US officials said.
"This is a BP mess, it is a horrible mess and it is a massive environmental mess," Mr Salazar said. He added BP was legally responsible for halting the spreading spill, cleaning up its effects and paying for resulting economic damages.
Mr Salazar said an ongoing investigation by US authorities would hold the company accountable "both civilly and in whatever way is necessary," appearing to leave open the possibility of a criminal inquiry.
The oil spill is a political hot potato for the Obama administration ahead of a November election that is widely expected to erode Democrats' control of the US Congress. Analysts warn that voters may punish Democrats regardless of who is ultimately deemed responsible for the mess.
The White House has repeatedly said it is the energy giant's responsibility to clean up the spill, but with public anger over BP's handling of the crisis intensifying, there have been calls for the Obama administration to take charge.
Reuters