"I urge them to seek more help from the federal government and others."

Barack Obama, the US president, will head to the region on Sunday for a first-hand update on the leak and efforts to protect the environment of the area.

Full impact awaited

With efforts to plug the leak so far unsuccessful and worsening weather in the coming days likely to further hamper attempts to plug the leak, fears are growing of an ecological disaster that could rival the 1989 Exxon Valdez spill in Alaska.

in depth

  Spill threatens sensitive coastline
  Blog: 'They saw it coming!'
  US fights Gulf oil spill
  Military to quell oil spill
  How the spill happened
  Environmental crisis looms
  Counting the cost:
  Oil exploration

Already the first birds coated in oil have been received by animal rescue centres, and wildlife groups are braced to receive many more casualties.

Al Jazeera's Sebastian Walker, reporting from Venice, Louisiana, said residents of the Gulf coast region are still waiting to see the worst effects of the spill.

"It's going to be some time before we really see the full impact in terms of animals being coated in oil and oil washing up on the shoreline."

But he said BP's failure to control the spill has raised concern and questions about the oil company's plan.

"There doesn't seem to be a plan in place for such type of spillage. BP is certainly taking a lot of flak, its safety record in the US isn't the greatest.

"But it's also the government that people are asking questions of. They're saying 'Why wasn't this flagged up earlier?' The government only declared this an event of national significance on Thursday but this spillage started to happen on April 20.

"There is a lot of blame being thrown around and questions of whether this response has been quick enough."

'Strongest possible response'

Recovery workers have been deploying miles of inflatable booms hoping to contain the oil, but strong winds and heavy seas have caused several of the barriers to break loose and washed them onto the shore.

Chemical dispersant is being used underwater in an attempt to tackle the oil as it leaves the broken riser, while remote-controlled subs were trying to activate a blow out preventer that should have blocked oil from flowing into the sea when the rig sank.


Growing oil disaster puts fragile coastal wildlife habitats under threat

"We will continue to push BP to engage in the strongest possible response," she said during a visit to Louisiana," Janet Napolitano, the US homeland security secretary, said on Friday.

Ken Salazar, the US interior secretary, who was travelling with Napolitano, said he had also pressed the chief executive of BP to "work harder and faster and smarter to get the job done".

The US government, he said, would not rest until BP seals the well and "they clean up every drop of oil".

The oil company has been accused of downplaying the risk of such a disaster in the Gulf of Mexico.

In a 2009 report, BP suggested that such an accident leading to a giant crude oil spill and serious damage to beaches, fish and mammals was unlikely and virtually impossible.

BP has now taken full responsibility for the oil spill, promising to pay for the clean-up and compensate people who have been affected.

But the company said it still does not know how the accident happened.

"We actually don't know what caused this event and clearly the government has an investigation that they've initiated," Doug Suttles, a chief operating officer at BP, said.

"We've launched our own internal investigation as well, but since this event began, we've only had one focus, which is to stop the flow of oil and minimise the impact."