Under pressure from President Barack Obama and the public to contain what could become the worst oil spill in US history, BP Plc today claimed full responsibility for the consequences of the spill in the Gulf of Mexico and promised to pay all legitimate claims and clean-up costs, dpa reported. Close to two weeks after the explosion on the Deepwater Horizon oil rig and its subsequent sinking, an 80-km-wide and 130-km-long oil slick edged towards the Louisiana shore, while efforts to stop the oil from gushing to the surface remained unsuccessful. BP said that drilling a relief well, which is crucial to plans to recap the leaking well, could take 90 days. Authorities estimate that the damaged well is spewing crude oil into the Gulf of Mexico waters at the rate of at least 5,000 barrels a day. The cause of the explosion has still not been determined. In Venice, Louisiana, a staging ground for efforts to fight the spill, Obama on Sunday warned of a "massive and potentially unprecedented environmental disaster," as the oil slick moved 7.5 kilometres off the coast of southeastern Louisiana. "The oil that is still leaking from the well could seriously damage the economy and the environment of our Gulf states and it could extend for a long time. It could jeopardize the livelihoods of thousands of Americans who call this place home," Obama said. A billboard on highway 23 en route to the area the president visited said simply: "Obama Send Help!" Many people here are already losing hope. Shrimp fisher Waylon Buras, 33, shrugged his shoulders in indifference when asked about Obama's assurances. "I want to see action," he said. He recalled how after the devastating January 12 earthquake in Haiti, Obama sent assistance in two days. But even close to two weeks after the explosion there has been no concrete financial help, he said, as his colleagues nodded in agreement. The National Oceanic and Atmospheric Administration (NOAA) on Sunday banned fishing in large parts of the Gulf of Mexico facing ecological damage. The ban, which affects both commercial and sport fishing, will last for 10 days. Buras murmured about all the promises and rumours, and said the oil industry had promised that everything would be safe. But now his boat, Miss Carmine, is grounded. "If local fishermen can't fish, then that's an economic loss that BP is going to have to pay," White House spokesman Robert Gibbs said Monday. "The economic damages that are incurred are part of the costs of this incident." Obama vowed Sunday that his administration would be "relentless" in its efforts to stop the leak at the source, and ensure the oil is cleaned up and people in the region are able to go back to their livelihoods. However, he also made it clear that BP would bear all the costs. "BP is responsible for this leak; BP will be paying the bill," he emphasized. BP said Monday its costs "may include claims for assessment, mitigation and clean-up of spilled oil, real and property damage caused by the oil, personal injury caused by the spill, commercial losses including loss of earnings/profit and other losses as contemplated by applicable laws and regulations." A BP spokeswoman confirmed estimates that current efforts to contain the spill and secure the well were costing about 6 million dollars per day. She said it was "far too early to quantify" the total cost of the damage. Experts warned Monday that the cost of clearing up the spill could run into billions of dollars. Alabama, Mississippi, Louisiana and Florida are facing the brunt of the ecological and economic disaster and have declared states of emergency. Response crews continue to test a new technique to break up the oil before it reaches the surface - a remotely operated underwater vehicle dispensing sub-surface dispersant at a rate of 34 litres per minute. This could stem three known leaks in the pipe from the wellhead, 1,500 metres deep on the sea floor. More than 152,400 metres of boom, or barriers to stop or slow the advance of oil, are in use. Nearly 2,000 personnel are currently responding to protect the shoreline, fragile shrimp beds and grassy marshes that line the Mississippi River delta, which provides a lush nursery for birds and marine life.