Louisiana (Reuters) - Energy giant BP Plc seeks to double the amount of oil it captures from its ruptured Gulf of Mexico well, while the U.S. Gulf Coast will be struggling with the environmental mess from the huge spill for years, the Coast Guard said on Monday.
The figure underscored some scientists' concerns that the May 27 government estimate of up to 19,000 barrels coming daily from the well a mile under the sea may be too low. BP had estimated the flow at just 5,000 barrels a day.
Neither Allen nor BP gave an estimate of how much oil is still flowing into the Gulf.
The 49-day-old spill is causing an ecological and economic disaster along the U.S. Gulf Coast, and testing Barack Obama's presidency.
BP's latest effort to contain the gushing oil is the first positive sign after a series of failed attempts fueled public anger at the company.
The earlier efforts generated initial optimism that an end to the crisis was in sight, but those hopes were dashed when the crude kept spewing out. Allen said BP's latest attempt -- placing a containment cap on top of the gushing pipe on the ocean floor -- appeared to be going "fairly well."
Allen said cleaning up the oil spill will take at least four to six weeks after the well is eventually sealed -- expected to be in August. But dealing with the long-term environmental effects will take years, he said.
"We're no longer dealing with a large, monolithic spill. We're dealing with an aggregation of hundreds of thousands of patches of oil that are going a lot of different directions," Allen said, stressing the broad dispersal of the oil.
"Dealing with the oil spill on the surface is going to go on for a couple of months" once the well is plugged, Allen said. "Long-term issues of restoring the environment and the habitats ... will be years."
Obama said after meeting with Cabinet officials at the White House that the economic impact of the spill, which threatens the Gulf Coast's multibillion-dollar fishing industry, will be substantial.
He said the U.S. government would "ride herd" on BP to make sure that it paid damage claims from Gulf Coast residents, who have complained that the company is not paying them promptly.
He was also pushing BP to be prepared for a possible hurricane in the Gulf. The Atlantic hurricane season, which is forecast to be unusually active this year, began last week, typically peaks in August and ends in November.
BP said it was preparing a system that, in case of a hurricane approaching, would allow the drillship collecting the oil to disconnect from a pipe that floats up to about 300 feet below the water's surface and get out of the storm's path. It is expected to be operational by early July.
BP shares, which have lost about a third of their value since the crisis began, closed slightly lower in London trading. In New York, BP's American depositary shares closed down 1.1 percent.
"With the right LMRP (containment cap) efficiency and surface skimming response, we may have turned the corner on shoreline oil spill volumes," analysts at Credit Suisse said in a research note.
But there were still signs of investor skepticism.
Goldman Sachs downgraded its rating on BP to "neutral" from "buy," saying the spill would impact the London-based company's ability to do business worldwide, while Nordic bank Nordea said it had divested all its BP shares, worth about 10 million euros ($12 million) from its funds.
Containing the spill is a critical test for BP and Obama.
Images of birds struggling through oil-soaked waters ringing Louisiana's ecologically fragile barrier islands and marshes have added to the pressure on Obama, who already faces growing public criticism over his handling of the crisis.
A new Washington Post/ABC poll found that 69 percent of Americans believe the government had done a "not so good" or "poor" job handling the spill. Just over 1,000 people were surveyed in the poll, conducted between June 3 and 6.
'THE BIG UNKNOWN'
The new BP effort involves placing a containment cap with a seal on remnants of a pipe at the deep-sea wellhead. Oil is channeled to a ship for later processing at a refinery ashore.
BP said it collected 10,500 barrels of oil on Saturday and 11,100 barrels on Sunday, with 27,700 barrels of oil collected between June 3, when the operation began, and June 6.
"We still don't know what the flow rate is. That's the big unknown right now," Allen said.
One high-end estimate by a U.S. government expert panel puts the leak at 25,000 barrels (1.05 million gallons/3.97 million liters) a day.
Allen said BP would send a second rig to the spill site to help capture the oil "and the combination of these two ... will have a production capability of about 20,000 barrels a day."
"Our aim is to capture all the oil, whatever that volume is," a BP spokesman said in response to Allen's statement, without confirming the figure given by the admiral.
A live video feed of the seabed leak shows black crude still billowing into the sea.
BP and government officials have said a definitive solution will not come until August when a relief well is drilled. This is intended to intersect the leaking well and allow it to be sealed.
After contaminating wetland wildlife refuges in Louisiana and barrier islands in Mississippi and Alabama, oil has begun to hit some of the famous white beaches of Florida, where the $60 billion-a-year tourism industry accounts for nearly 1 million jobs.
As clean-up crews raked up oil debris and oiled seaweed on Pensacola Beach in the northwest Florida Panhandle, visitors seemed undeterred by the pollution threat.
"It's an awful crisis but we're really not going to let it ruin our vacation," said Jennifer Blow from New Orleans.
One-third of the Gulf's federal waters, or 78,000 square miles (200,000 square km), remains closed to fishing, and the toll of dead and injured birds and marine animals is climbing.
(Additional reporting by Bruce Nichols in Houston, Tom Brown in Miami, Jeff Mason, Matt Spetalnick in Washington, Tom Bergin in London; writing by Pascal Fletcher and Ross Colvin; editing by Will Dunham and Mohammad Zargham)