Preparing the country for the possibility of even worse news, the Obama administration on Sunday warned that BP's next effort to contain the oil spewing from a damaged well in the Gulf could result in a temporary 20 percent increase in the flow.
BP's latest attempt to stem the leak involves cutting and removing a damaged pipe.
White House energy czar Carol Browner said in a news release Sunday that government scientists believe the oil gusher could increase as much as 20 percent from the time the pipe is cut to when a containment valve is in place.
BP spokesman John Curry did not know how much time would pass between the procedures. The operation began Saturday and is expected to take four to seven days.
BP PLC Chief Operating Office Doug Suttles said Saturday that cutting off the damaged pipe wasn't expected to cause the flow to increase significantly.
Earlier Sunday, BP's managing director said on NBC's "Meet the Press" that BP is optimistic its latest attempt could show results by the end of the week.
The new strategy is being tried after company abandoned its most ambitious bid yet for a temporary fix Saturday when BP said the “top kill” option — an attempt to overwhelm the broken well with heavy fluids and junk — had failed.
That strategy, which sought to stop the flow of oil, was always a long shot, Robert Dudley, the company’s managing director and head of disaster management, told NBC’s David Gregory on Sunday.
The probability is “much better” that the new approach, which seeks to contain the spread of the oil, will show good results this week, he said.
“I think the engineering on this is more simple than the top kill,” Dudley said.
BP hopes to use a diamond-cut saw to slice through a pipe leading out from the well and cap it with a funnel-like device using the same remotely guided undersea robots that have failed in other tries to stop the gusher, Dudley said.
“We have to do everything by robot” because the leak originates 5,000 feet below the surface, he said. “They have to go down and construct a small city.”
'Worst environmental disaster'
The spill has dumped 18 million to 40 million gallons into the Gulf, according to government estimates, exceeding even the 1989 Exxon Valdez disaster off the coast of Alaska. The leak began after the Deepwater Horizon drilling rig exploded in April, killing 11 people.
“This is without doubt the worst environmental disaster in our history,” Browner said on “Meet the Press.”
Experts have said a bend in the damaged riser likely was restricting the flow of oil somewhat, so slicing it off and installing a new containment valve is risky.
“If they can’t get that valve on, things will get much worse,” said Philip W. Johnson, an engineering professor at the University of Alabama.
Johnson said he thought BP could succeed with the valve, but he added: “It’s a scary proposition.”
News that the top kill fell short drew a sharply worded response Saturday from Obama, a day after he visited the Gulf Coast to see the damage firsthand.
“It is as enraging as it is heartbreaking, and we will not relent until this leak is contained, until the waters and shores are cleaned up and until the people unjustly victimized by this manmade disaster are made whole,” Obama said.
In the days after the spill, BP was unable to use robot submarines to close valves on the massive blowout preventer atop the damaged well. Then, two weeks later, ice-like crystals clogged a 100-ton box the company tried placing over the leak. Earlier this week, engineers removed a mile-long siphon tube after it sucked up only 900,000 gallons of oil from the gusher.
BP CEO disputes plumes reports
Also Sunday, BP Chief Executive Officer Tony Hayward disputed claims by scientists that large undersea plumes have been set adrift by the Gulf oil spill and said the cleanup fight has narrowed to surface slicks rolling into Louisiana's coastal marshes.
During a tour of a company staging area for cleanup workers, Hayward said BP's sampling showed "no evidence" that oil was suspended in large masses beneath the surface. He didn't elaborate on how the testing was done.
"The oil is on the surface," Hayward said. "Oil has a specific gravity that's about half that of water. It wants to get to the surface because of the difference in specific gravity."
Scientists from several universities have reported plumes of what appears to be oil suspended in clouds stretching for miles and reaching hundreds of feet beneath the Gulf's surface.
Those findings — from the University of South Florida, the University of Georgia, Southern Mississippi University and other institutions — were based on initial observations of water samples taken in the Gulf over the last several weeks. They continue to be analyzed.
One researcher said Sunday that their findings are bolstered by the fact that scientists from different institutions have come to similar conclusions after doing separate testing.
"There's been enough evidence from enough different sources," said Marine scientist James Cowan of Louisiana State University, who reported finding a plume last week of oil about 50 miles from the spill site that reached to depths of at least 400 feet.