Oil from a giant slick washed ashore in Louisiana Friday, threatening a catastrophe for the US Gulf Coast as the government called a national diasaster and mulled sending in the military. With up to 200,000 gallons of oil a day spewing into the Gulf of Mexico from a leaking well, the accident stemming from a sunken offshore rig threatens to rival the Exxon Valdez disaster as the worst oil spill in US history. Duration: 01:49