The US administration has banned oil drilling in new areas of the US coast while the cause of the oil spill off Louisiana is investigated.

White House adviser David Axelrod told ABC TV they wanted to know exactly what led to last week’s explosion on the BP-operated rig in the Gulf of Mexico.

Last month President Barack Obama eased a moratorium on new offshore drilling.

Up to 5,000 barrels of oil a day are thought to be spilling into the water, threatening US coastal areas.

The slick has begun to reach the Louisiana shore, and the US Navy has been sent to help avert an economic and environmental disaster.

‘Mind-boggling’

Mr Axelrod announced the ban on drilling in new areas in an interview with ABC’s Good Morning America programme on Friday.

He also defended the administration’s response to the 20 April explosion that destroyed the Deepwater Horizon rig, saying “we had the coast guard in almost immediately”.

The US government has designated the Gulf of Mexico oil spill as an “incident of national significance”. This allows it to draw on resources from across the country.

The wetlands off the Louisiana coast sustain hundreds of wildlife species and a big seafood and fishing industry.

Governor Bobby Jindal has declared a state of emergency and asked for federal funds to deploy 6,000 National Guard soldiers to help with the clean-up.

The US Coast Guard said it had sent investigators to confirm whether crude oil had begun to wash up on parts of the Louisiana shoreline.

Cdr Mark McCadden, of the coast guard, told the BBC they were using all resources available.

“We’re putting everything forth in plans for a worst-case scenario,” he said.

“We can always ramp back on some of those resources, but right now the priority is to bring as many resources as are available to attack this spill and try to minimise the effects to the coast and to the public.”

Two US Air Force planes have been sent to Mississippi in case they are needed to spray oil-dispersing chemicals over the slick.

David Kennedy of the National Oceanic and Atmospheric Administration described the oil spill as a “very, very big thing”.

The clean-up efforts could be “mind-boggling”, he told the Associated Press news agency.

The Louisiana coastline, with its rich shrimp and oyster beds, is the most threatened by the spill.

There are also fears of severe damage to fisheries and wildlife in Mississippi, Alabama and Florida as oil continues to escape from the wreckage of the rig.

An emergency shrimping season was opened on Thursday to allow fishermen to bring in their catch before it was fouled by the advancing oil.

Navy vessels are helping to deploy booms to contain the spill.

‘Very, very difficult’

President Obama has dispatched high-level administration officials, including Homeland Security Secretary Janet Napolitano, to the area.

He said they would “ensure that BP and the entire US government is doing everything possible, not just to respond to this incident, but also to determine its cause”.

Speaking at the White House, Mr Obama also said: “While BP is ultimately responsible for funding the cost of response and clean-up operations, my administration will continue to use every single available resource at our disposal, including potentially the Department of Defence, to address the incident.”

Eleven workers are still missing, presumed dead, after the Deepwater Horizon rig exploded on 20 April.

BP’s chief operating officer of exploration and production, Doug Suttles, said the company was using remotely operated vehicles (ROVs) to try to find out how much oil was leaking into the sea.

“This is very, very difficult to estimate,” Mr Suttles told reporters.

“Down below the surface we actually can’t meter this oil so we can just observe it… what our ROV pictures show to us on the sea floor hasn’t changed since we first saw the leak… but what we can say based on what we’re picking up on the surface it looks like it is more.”

Mr Suttles put the oil leakage at between 1,000 and 5,000 barrels a day.

BBC NEWS