A rain-soaked President Obama delivered a somber message from a Coast Guard station on Louisiana's threatened coastline. "We are dealing with a massive and potentially-unprecedented environmental disaster. 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," he said.

The president was accompanied by Louisiana Governor Bobby Jindal, Mr. Obama said that even while hoping for the best, the federal government is prepared for a worst case scenario, if the spill from the underwater well continues. He promised a full investigation of the disaster, and said that petroleum giant BP will be held responsible for the accident. But for now, he said, there is work to be done. "Every American affected by this spill should know this: Your government will do whatever it takes for as long as it takes to stop this crisis," he said.

An explosion nearly two weeks ago aboard the now-sunken oil rig killed 11 workers. The U.S. Coast Guard says millions of liters of oil have since spilled into the Gulf of Mexico.

Appearing on ABC television's "This Week" program, the chairman of BP America, Lamar McKay, said there is no way to know just how much oil is flowing into the Gulf of Mexico. "I do not know the volume. The volume is uncertain. There is a large uncertainty range around the 5000 barrels. Our spill response is designed to take that uncertainty into account," he said.

Federal officials say stopping the oil flow could take weeks or even months.

U.S. Interior Secretary Ken Salazar also appeared on "This Week." "Hopefully something will happen. Best case scenario - it gets stopped today. Worst case scenario - this thing could keep going on for 90 days," he said.

The oil slick threatens ever-larger swaths of the U.S. coastline, placing sensitive marine ecosystems in peril. If uncontained, experts say oil could saturate beaches and marine habitats as far away as Florida, devastating fishing and tourism.

The disaster comes as Obama administration attempts to chart a course toward U.S. energy independence and less reliance on fossil fuels. President Obama endorsed more off-shore drilling as part of a comprehensive strategy, but he has since halted new drilling projects until investigators determine the cause of the BP accident.

coast guard:海岸护卫队

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（来源：VOA 编辑：陈丹妮）