Oil from a wrecked offshore drilling platform oozed into the marshes of southernmost Louisiana today, coating birds and threatening to create America's worst environmental disaster in two decades.
The oil began washing ashore near the mouth of the Mississippi River. Louisiana is home to 40 percent of the United States' wetlands and the oil now threatens some 400 species of animals, from shrimp to pelicans to river otters.
Meanwhile, the White House announced Friday that there will be no new offshore drilling until there is an "adequate review" of what happened.
"I continue to believe that domestic oil production is an important part of our overall strategy for energy security," said President Obama in a statement from the Rose Garden, "but I've always said it must be done responsibly, for the safety of our workers and our environment."
On ABC's "Good Morning America," White House senior adviser David Axelrod defended the administration's stance, but said it would need a fresh look in light of last week's disaster.
"No additional drilling has been authorized and none will until we find out what happened here and whether there was something unique and preventable here," Axelrod told George Stephanopoulos.
Members of the president's cabinet are descending on the region to observe the efforts to contain the massive oil spill that continues to leak thousands of barrels a day into the Gulf.
Department of Homeland Security Secretary Janet Napolitano, Department of the Interior Secretary Ken Salazar and Environmental Protection Agency Administrator Lisa Jackson are taking an aerial tour of the spill before an afternoon media briefing.
The oil is leaking at a rate of up to 210,000 gallons per day, according to an estimate from the National Oceanic and Atmospheric Administration. At that rate it would surpass the Exxon Valdez spill, which released a total of 11 million gallons of oil, in approximately 55 days, according to Nancy Kinner, the co-director of Co-Director of the Coastal Response Research Center at the University of New Hampshire.
Overnight BP said it would make another attempt to stop the flow of oil by pumping chemical dispersants down to the Gulf floor to break up the oil at the well, a method that has never been used a mile underwater.
"That is a technology that is in new stages and we are working closely with our scientific support from NOAA to analyze what the impact of that dispersant technology will be. And there will be very careful scrutiny but if it has applicability, which we think it does, we want to get that in place very quickly," Coast Guard Rear Admiral Sally Brice-O'Hara said on "Good Morning America."
The response team has been using dispersants, skimming and a controlled burn in an effort to control the spill. However, Brice-O'Hara said because of rough weather the skimming and controlled fires would be impossible today.
BP says it is pressing ahead with a plan to collect the leaking oil with a dome placed over the well. It is also working to drill a relief well to stop the flow, though it concedes that could take months.
Oil Spill Event of 'National Significance'Yesterday Louisiana Governor Bobby Jindal requested the assistance of the Louisiana National Guard to help with the response efforts. He declared a state of emergency because of the oil slick.
Meanwhile in Washington, the Obama administration labeled the spill as an event of "national significance."
"While BP is ultimately responsible for funding the cost of response and cleanup operations, my administration will continue to use every single available resource at our disposal, including potentially the Department of Defense to address the incident," President Obama said.
Napolitano said during a White House briefing Thursday that designating the spill as one of "national significance" means that "we can now draw down assets from across the country" to assist with cleanup.
She said 1,100 people are working on the cleanup effort, which so far has collected 685,000 gallons of oil and water from the polluted Gulf.
The White House said 174,060 feet of flotation booms had been deployed to corral the floating oil. It said an additional 243,260 feet is available and 265,460 feet has been ordered.
It said 76 tugs, barges and skimmers were on scene to help in containment and cleanup, along with six fixed-wing aircraft, 11 helicopters, 10 remotely operated vehicles, and two mobile offshore drilling units.
Louisiana shrimpers filed a class-action lawsuit against BP, the owners of the oil rig, and the Halliburton company, which they say was working to cement the rig's well and well-cap. The suit claimed that these companies and others were negligent in allowing the explosion that led to the spill, which they claim now threatens their livelihoods. They are asking for damages of at least $5 million.
Jindal said BP had agreed to allow local fishermen to assist in the expected cleanup. Under the agreement, shrimpers and fishermen could be contracted by BP to help. Jindal said the state was also training prison inmates to help clean up wildlife harmed by oil slicks moving toward shore.
Billy Nungesser, the president of Plaquemines Parish, the county closest to the spill, said he thought BP underestimated what's about to come ashore and are only asking for help now that it may be too late.
"We know the weather's coming. We know the wind is going to be 25 to 30 knots coming, blowing that oil into the bayous," he said. "Somebody's got to be able to draw a line in the sand."
Gulf of Mexico Oil Spill
BP's Chief Operating Officer, Douglas Suttles, admitted some responsibility for the disaster "because we're the lease holder," but assigning blame, he said, should come after the cleanup.
"I can tell you we're not worried about that right now," he said Thursday. "Who's ultimately responsible for what will come out over time through an investigations process."
Suttles said the rig was equipped with some safety devices that should have prevented this kind of spill.
"They didn't do that, we don't know why they didn't do that and ultimately we will find out," he said.
Suttles was quick to point out that another company was operating the rig at the time of the explosion, not London-based BP.
"I can say that we had equipment required by the regulations," he said. "We don't know why, when the accident occurred, and I should probably clarify, the lease we are drilling on is owed by BP and a few other companies."
One ray of hope is that about 30 percent of an oil slick usually evaporates in the strong southern sun, and microbes and waves take care of another large portion.
"Mother nature does a much better job at cleaning up than we do of picking up," said Ed Levine, an oceanographer with the National Oceanographic and Atmospheric Administration.
Gulf of Mexico Oil Spill
The Deepwater Horizon drilling rig, operated by BP Oil and owned by Transocean Ltd., exploded and started burning April 20. Eleven rig workers were never found and are presumed to have died.
Oil from the area is called light sweet crude, but Edward Overton, a professor emeritus of environmental science at Louisiana State University, said the name is deceptive. It contains heavy compounds, called asphaltenes, that do not burn easily or evaporate, even in the warm climate off Louisiana.
"When you've got a spill like this," said Overton, "there are three things you can do. You can burn it, scoop it up out of the water, or use chemical dispersants to break it up. This oil is not particularly good with any of those three."
"With light crude," he said, "you could burn most of it -- 70 or 80 percent. With heavy crude, I don't know. I'm not optimistic."
ABC News' Matt Gutman and Jake Tapper provided additional information. ABC News Radio and The Associated Press contributed to this report.