Oil slick closes on U.S. coast, BP pressed to act

VENICE, Louisiana (Reuters) - A huge wind-driven oil slick bore down on the U.S. Gulf coast on Sunday, threatening an environmental catastrophe, and the Obama administration heaped pressure on BP Plc to halt the uncontrolled spill from its ruptured Gulf of Mexico well.

Since the explosion and sinking last week of the Deepwater Horizon rig, a disaster scenario has emerged with hundreds of thousands of gallons of crude oil spewing unchecked into the Gulf and moving inexorably northward to the coast.

The spreading black tide threatens wildlife, beaches and one of the world's most fertile fishing grounds in an area stretching across four states, from Louisiana to Florida.

President Barack Obama, seeking to deflect criticism that his government was slow in responding to what looks like the biggest oil spill in U.S. history, was travelling on Sunday morning to Louisiana.

No doubt mindful of public criticism of President George W. Bush's handling of the 2005 Hurricane Katrina disaster, Obama is keen to show his government is acting quickly to deal with an accident that could rival the 1989 Exxon Valdez catastrophe in Alaska, the worst previous U.S. oil spill to date.

Desperate efforts above and below the ocean surface -- using boats, planes and even an underwater robotic vehicle -- to check the oil flow and disperse and contain the spreading slick were being badly hampered by high winds and rough seas.

After initially stressing cooperation with BP, Obama administration officials have in recent days made clear their frustration with the London-based company, urging it to do more to seal the blown-out wellhead and shut off the oil.

"Our job basically is to keep the boot on the neck of British Petroleum to carry out the responsibilities they have both under the law and contractually to move forward and stop this spill," U.S. Interior Secretary Ken Salazar told CNN's "State of the Union" program.

But officials from BP, which faces billions of dollars in cleanup costs and lawsuits, said shutting off the well almost 1 mile (1.6 km) down on the ocean floor is a hugely complicated operation that could take weeks and even months, not days.

"OPEN-HEART SURGERY IN THE DARK"

It was like performing "open heart surgery at 5,000 feet in the dark with robot-controlled submarines," BP America Chairman and President Lamar McKay told ABC News' "This Week" program.

The Mail, a British newspaper, said the spill could cost BP over 3 billion pounds ($4.6 billion) in containment and clean-up expenses.

Shares of BP and other companies involved in operating the lost rig plummeted last week as fears mounted of growing financial costs and legal liability from the accident.

Alarm over the potential ecological disaster has grown as it has become clear that nobody knows how much oil is gushing from the ruptured wellhead.

Interior Secretary Salazar said that in a worst case scenario the blown-out well could gush 100,000 barrels (4.2 million gallons or 15.9 million litres) or more of oil per day -- a huge increase over existing official estimates of only 5,000 barrels per day.

"The actual amount is impossible to estimate," Doug Suttles, chief operating officer of BP's exploration and production unit, said on the "Today" show.

Salazar said there was "no doubt" a mechanism that should have prevented oil from blowing out of the well was defective. He also said it could be 90 days before a relief well was completed that could shut off the flow.

BP was working to fit a containment mechanism over the leaking wellhead.

The three containment chambers are giant box-shaped inverted funnels designed to cover the well and two other leaks and channel the oil to a drillship. McKay said a containment dome was in the final engineering phase and he expected it to be deployed to the site in six to eight days.

The spill has forced Obama to suspend politically sensitive plans to expand offshore oil drilling, unveiled last month partly to woo Republican support for climate legislation, one of the U.S. leader's priorities.

WEATHER NOT COOPERATING

National Oceanic and Atmospheric Administration (NOAA) forecasts showed the spill heading towards the Louisiana, Mississippi and Alabama coasts.

The projection indicated the possibility of some oil beaching on Sunday on the Chandeleur Islands on the fringe of the Mississippi Delta. The outlying islands are the site of the Breton National Wildlife refuge, home to major bird colonies.

The Gulf Coast is home to hundreds of species of wildlife, including manatees, sea turtles, dolphins, porpoises, whales, otters, pelicans and other birds.

It also teems with shrimp, oysters, mussels, crab and fish, supporting a $1.8 billion (1.2 billion pounds) seafood industry that is second only to Alaska.

The disaster came as BP was still working to repair its reputation in the United States in the wake of a 2005 blast at a Texas refinery that killed 15 workers, and a major oil spill in Alaska in 2006 that was blamed on corroded pipelines.

The two incidents cost BP billions of dollars and drew considerable scrutiny from U.S. politicians and regulators.

Although the Coast Guard has laid hundreds of thousands of feet of protective booms to try to halt the encroaching oil, high winds and rough seas were badly hampering the deployment of the plastic barriers and efforts by boats and planes to spray chemical dispersant on the oil.

"The weather is very, very hard right now to contain the spill offshore. We are able to use dispersants, but we are not able to use our booms and skimmers," BP's Suttles said.

The Louisiana Department of Wildlife and Fisheries closed recreational and commercial fishing in areas of likely impact, according to the NOAA web site. The Louisiana Department of Health and Hospitals closed oyster harvesting areas in the coastal parishes of Plaquemines and St. Bernard.

Many of the communities in the path of the oil slick are the same ones devastated by Hurricane Katrina.

"There's enough oil out there that it is logical to think it will hit the shoreline. It's just a question of where and when," U.S. Coast Guard Admiral Thad Allen said on Saturday. "Mother Nature gets a vote in this thing.

So far, vital shipping lanes leading to the Mississippi River and huge Gulf Coast ports have not been affected, officials said.

In the first sign the spill has affected U.S. offshore energy production, the Minerals Management Service said on Saturday two U.S. offshore Gulf of Mexico production platforms had been shut down and a third was evacuated as a safety precaution. Further shutdowns were possible, it added, but the output affected so far was very small.

(Additional reporting by Paul Simao in Washington, Chris Baltimore, Anna Driver and Kristen Hays in Houston, Tom Bergin in London, Carlos Barria in Venice, Louisiana, Phil Stewart in Washington, Joshua Schnyer and Rebekah Kebede in New York; Writing by Pascal Fletcher; Editing by Paul Simao)