A sandpiper on the shore of one of the Chandeleur islands. The Deepwater Horizon oil spill threatens this beach and all of its wildlife. Photograph: Gerald Herbert / AP via guardian.co.uk

By Chris McGreal in Washington, Terry Macalister and Adam Gabbatt 
www.guardian.co.uk, Thursday 29 April 2010 20.16 BST The United States mobilised its military tonight in an attempt to help deal with the vast oil slick spreading across the Gulf of Mexico amid predictions that it will begin to hit the Louisiana coast within hours and could cause one of the country’s biggest environmental disasters. The US coastguard said today that oil was flowing into the sea at five times the rate previously estimated. The government has taken broad control of efforts to contain the spill from last week’s blowout on the Deepwater Horizon rig, with the White House saying it had imposed “oversight” of BP’s efforts and is pursuing an “aggressive” response that includes mobilising naval ships. Louisiana has declared a state of emergency and the White House said the president, Barack Obama, and the joint chiefs of staff were being briefed regularly on the situation. Tonight, Obama said the British company was “ultimately responsible” for the spill. The reassessment of the scale of the disaster, which came after a third leak was discovered, sent BP’s share price plunging, with more than £13bn knocked off the company’s market value since the explosion. Under US law, the company is responsible for the costs of dealing with the crisis, including paying for use of the military. Environmentalists warned that the spill, which covers an area about the size of Cornwall and is just a few miles off the Mississippi river delta, could turn out to be as catastrophic as the impact of the Exxon Valdez tanker spill off Alaska was 21 years ago. The most immediate threat is to birds, dolphins and turtles in the area and to the Louisiana coast, as strengthening winds push the slick toward the shore. Environmentalists say the oil is likely to hit the delta and a series of barrier islands that have still not fully recovered from hurricane Katrina six years ago and which are home to more than 400 species. But if the oil continues to spread it could hit Mississippi, Alabama and Florida. …

Deepwater Horizon oil slick to hit US coast within hours