NEW YORK: Oil from a giant slick has washed ashore in Louisiana, threatening a catastrophe for the US Gulf Coast as the government declared national disaster and considered sending in the military.With up to 900,000 litres of oil a day spewing into the Gulf of Mexico from a ruptured well, experts warned it could prove to be the world’s worst offshore spill.Strong south-east winds blew the first oily strands of the slick – which has a circumference of 1550 kilometres – directly on to the wetlands of South Pass near the mouth of the Mississippi River late on Thursday, local officials said.Hundreds of kilometres of coastline in Louisiana, Mississippi, Alabama and Florida were under imminent threat.With BP, which leases the wrecked rig, no closer to capping the well, the White House adopted emergency measures to try to avoid the kind of disaster that Hurricane Katrina wrought on the Gulf Coast in 2005.The President, Barack Obama, said he would send senior members of his cabinet, including his homeland security, environment and interior secretaries, to survey the site.”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,” Mr Obama said.The administration is well aware that Mr Obama’s victory in the 2008 presidential election was built in part on a belief among voters that he would do a better job at responding to disasters than George Bush did to Katrina.The Homeland Security Secretary, Janet Napolitano, said the spill was a disaster of ”national significance”. She said a command centre would be opened in Mobile, Alabama, in addition to the one in Louisiana. The US Navy said it had sent 20,000 metres of inflatable boom and seven skimming systems to the area. Both are used to control the movement of spills.White House officials said they began holding regular conference calls with BP executives soon after the accident.BP, which says it has been spending $US6 million ($6.5 million) a day on its own efforts, is already facing a class-action lawsuit brought by two Louisiana shrimp fishermen who are seeking at least $US5 million in damages for alleged negligence.The slick could cause severe environmental damage to beaches, wildlife and estuaries in four states.Rear Admiral Mary Landry, of the Coast Guard, who is leading the US response, said: ”It is premature to say this is catastrophic. I will say this is very serious.”However, Mike Miller, who runs Safety Boss, a Canadian oil well firefighting company, said the spill ”could be right up there, if not the biggest ever”.He said the Exxon Valdez disaster in 1989, in which a tanker spilt 41 million litres of oil into Prince William Sound, Alaska, would ”pale into insignificance in comparison to this as it goes on”.Mr Miller, whose company extinguished 180 of the 600 oil fires lit by Saddam Hussein’s retreating forces in Kuwait after the Gulf War, said the slick bore comparison with the Kuwait fires but was likely to be far more environmentally damaging as it was at sea rather than in a desert.The spill followed an explosion and fire on the Deepwater Horizon drilling rig on April 20 in which 11 workers are presumed to have died.Telegraph, London; The Washington Post, Agence France-Presse