A huge spreading oil spill in the Gulf of Mexico washed up to coastal Louisiana wildlife and seafood areas on Friday and the US government and military struggled to avert what could become one of the nation's worst ecological disasters.
With leading edges of the slick lapping up to outlying marshes and waterways on the fringes of the Mississippi Delta, the Coast Guard deployed protective equipment called booms along the coast in a bid to stop oil from soiling the shore.
Oil is pouring out of a blown-out undersea well off Louisiana at a rate of up to 5,000 barrels (210,000 gallons or 955,000 litres) a day. Forecasters say the spill could affect Mississippi, Alabama and northwest Florida in coming days.
Fitch's Energy Team estimated containment and clean-up costs could reach $2 billion to $3 billion "once the leak reaches land, and potentially more, the longer it takes to arrest the flow of oil into the Gulf," team senior director Jeffrey Woodruff said.
"We continue to bring every asset to bear to fight this spill," Coast Guard Rear Admiral Sally Brice-O'Hara told CNN.
The Coast Guard said it had received reports from the public of oil coming ashore in Louisiana's Pass-a-Loutre wildlife reserve, but it was awaiting its own confirmation.
At President Barack Obama's urgent request, Department of Homeland Security Secretary Janet Napolitano, Interior Secretary Ken Salazar and Environmental Protection Agency Administrator Lisa Jackson were due to fly over the affected Gulf area on Friday to assess the situation.
The accident forced Obama to put a hold on politically sensitive plans to expand offshore US oil drilling. He unveiled plans in March for a limited expansion, in part to try to win Republican support for climate change legislation.
The White House said no new drilling would be allowed until a review was conducted of the spill, which happened after an offshore rig exploded and sunk last week.
Obama has pledged to use every resource, including the US military, to contain the 120-mile (193-km) wide slick, while making clear that London-based BP, the owner of the ruptured well, was responsible for the cost of the clean-up.
BP'S Chief Executive Tony Hayward said the company would clean up the oil spill and compensate those affected.
"We are taking full responsibility for the spill... We are going to be very, very aggressive in all of that," he told Reuters in an interview on Friday.
Shares of oil services companies tumbled on Friday in the aftermath of the spill. BP is down around 12 per cent and Transocean down nearly 15 per cent since the rig explosion on April 20.