ROBERT, La. -- After failing again to stem the flow of oil into the Gulf of Mexico, BP scrambled Sunday to make some progress in ending the spill that the president's top energy adviser said was the biggest environmental disaster the U.S. has ever faced.
Six weeks after the spill, oil giant BP PLC said that its latest plan to cap the well wouldn't capture all the crude fouling the Gulf. And the relief wells currently being drilled -- which are supposed to be a better long-term solution -- won't be done for at least two months.
That would be in the middle of the Atlantic hurricane season, which begins Tuesday. The crude likely won't affect the formation of storms, but the cyclones could push the oil deeper into coastal marshes and estuaries and turn the oil into a crashing black surf.
White House energy adviser Carol Browner said Sunday on NBC's "Meet the Press" that there was more oil spilling into the Gulf than at any other time in history.
"This is probably the biggest environmental disaster we've ever faced in this country," Browner said.
The effort to curb that disaster known as the "top kill" failed after engineers tried for three days to overwhelm the crippled well with heavy drilling mud and junk 5,000 feet underwater.
Robert Dudley, BP's managing director, said on "Fox News Sunday" that company officials were disappointed that they "failed to wrestle this beast to the ground." But skepticism is growing that BP can solve the crisis.
Rep. Ed Markey, D-Mass., who leads a congressional committee investigating the disaster, told CBS' "Face the Nation" on Sunday that he had "no confidence whatsoever in BP."
"So I don't think that people should really believe what BP is saying in terms of the likelihood of anything that they're doing is going to turn out as they're predicting," he said.
BP hopes to saw 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. Even that effort won't end the disaster -- BP officials have only pledged it will capture a majority of the oil. None of the remaining options would stop the flow entirely or capture all the crude before it reaches the Gulf's waters.
Engineers will use remotely guided undersea robots to try to lower a cap onto the leak after cutting off part of a busted pipe leading out from the well. The funnel-like device is similar to a huge containment box that failed before when it became clogged with icelike slush. Dudley said officials learned a lot from that failure and will pump warm water through the pipes to prevent the ice problems.
The spill is the worst in U.S. history -- exceeding even the 1989 Exxon Valdez disaster -- and has dumped between 18 million and 40 million gallons into the Gulf, according to government estimates. The leak began after the Deepwater Horizon drilling rig exploded in April, killing 11 people.
"This scares everybody, the fact that we can't make this well stop flowing, the fact that we haven't succeeded so far," BP Chief Operating Officer Doug Suttles said Saturday. "Many of the things we're trying have been done on the surface before, but have never been tried at 5,000 feet."
He said cutting off the damaged riser isn't expected to cause the flow rate of leaking oil to increase significantly.
However, Browner said Sunday on CBS' "Face the Nation" that cutting the pipe could send more oil flowing into the Gulf -- up to 20 percent more than is currently spewing. That's because engineers will cut off a kink in the pipe that currently seems to be holding back some of the gusher, Browner said.
Browner also said how much oil the new cap can collect depends on how well it's fitted over the leak. Other experts also have said installing the new containment valve is risky because of the bend in the riser pipe.
"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.
Word that the top kill had failed hit hard in fishing communities along Louisiana's coast, where the impact has been underscored by oil-coated marshes and wildlife.
The top official in coastal Plaquemines Parish said news of the top kill failure brought tears to his eyes.
"They are going to destroy south Louisiana. We are dying a slow death here," said Billy Nungesser, the parish president. "We don't have time to wait while they try solutions. Hurricane season starts on Tuesday."
Associated Press Writers Matthew Brown, Janet McConnaughey and Mary Foster in New Orleans and AP Radio correspondent Shelly Adler contributed to this report.