On Friday, U.S. President Barack Obama visited a beach on the Gulf Coast affected by the enormous oil spill 80 kilometres offshore, and reassured residents that he was making the disaster cleanup his "highest priority."
"The situation remains the same since the day I visited Louisiana nearly four weeks ago," Obama told reporters while visiting the town of Grand Isle, Lousiana.
"It's an assault on our shores, on our people, on the regional economy and on communities like this one," he said. "People are watching their livelihoods wash up on the beach."
"We're going to keep at it," Obama said, referring to the massive cleanup effort that now involves some 20,000 workers.
Meanwhile, the head of BP acknowledged that the oil spill had become an "environmental catastrophe."
Tony Hayward, chief executive officer of BP PLC, had previously characterized the environmental impact of the spill as modest.
Hayward said Friday that it will take another two days to tell if the company's latest attempts to stop the flow of crude oil from its leaking well will succeed.
He said in 48 hours the company should know if it has succeeded with its so-called "top kill" procedure, pumping heavy drilling mud into the leaking well, 1,500 metres beneath the surface.
"Clearly I'm as anxious as everyone in America is to get this thing done," Hayward told the CBS Early Show.
The BP well has been spewing oil into the Gulf since April 20, when the Deepwater Horizon drilling rig exploded, killing 11 workers.
New government estimates say the resulting leak has now surpassed the Exxon Valdez disaster as the biggest oil spill in U.S. history.
The president's visit comes 38 days into the disaster and one day after a White House news conference where he asserted responsibility over the spill.
BP has said the top kill is progressing as planned, although Brad Bass, of the centre for environment at the University of Toronto, told CTV's Canada AM that the entire process is uncertain because it has never been tried so deep underwater.
"The top kill strategy has worked in shallow waters, but now you're a mile beneath the ocean. That far deep you have a lot more pressure, you have different temperatures and so we're really running an experiment," Bass said.
He said that early indications were positive, but said it was troubling that an experimental procedure appears to be the only way to stop an environmental catastrophe. "We're doing something that we don't know if it's going to work ... really we're running an experiment in uncharted waters."
The top kill is the latest in a string of attempts to stop the oil leak and if it works, BP will inject cement into the well to seal it permanently. If it doesn't, the company says it has a number of backup plans.
BP Chief Operating Officer Doug Suttles said the company is also considering shooting small, dense rubber balls or assorted junk such as golf balls and rubber scraps to stop up a crippled five-storey high piece of equipment known as a blowout preventer to keep the mud from escaping.
Permanent solution a long way off
Crews are continuing to drill a pair of relief wells, a process that could take several more weeks, as a permanent solution to the leak.
Meanwhile, a team of government scientists said the oil has been flowing at a rate up to five times higher than the company and the U.S. Coast Guard had previously estimated.
Two teams of scientists calculated the well has been leaking between 504,000 and more than a million gallons a day, meaning at least 18 million gallons have spilled so far.
In the worst-case scenario, 39 million gallons have leaked.
When the Exxon Valdez oil tanker ran aground in Alaska in 1989, it spilled nearly 11 million gallons.
"Now we know the true scale of the monster we are fighting in the Gulf," said Jeremy Symons, vice president of the National Wildlife Federation. "BP has unleashed an unstoppable force of appalling proportions."
BP officials said their previous estimate was based on the best data available at the time and that the company was not trying to mislead the public.
But residents of nearby coastal communities are bracing for an environmental catastrophe.
Globs of sticky brownish oil have been drifting onto shorelines and marshes from Alabama to Louisiana, covering pelican rookeries, oyster beds and shrimp nurseries.
Long, slender booms and other barriers intended to protect the shoreline have been unable to stop the creeping crude.
Tourism is 'dead' in Louisiana
Fishermen, hotel and restaurant owners, politicians and residents along the 150-kilometre stretch of coast affected by the spill say they are fed up with BP's failures to stop the spill.
"Tourism is dead. Fishing is dead. We're dying a slow death," said Charlotte Randolph, president of Louisiana's Lafourche Parish.
Two workers who were injured in the explosion have told the U.S. Congress that the companies in charge of the drilling operation had cut corners and neglected maintenance in a race toward higher profits.
Bass said a lax regulatory environment may have set the contitions for the disastrous spill.
"BP assured everyone that they had the situation well in hand; they were prepared for an accident (and) it was a low probability event," he said. "But it did happen and we really were caught unprepared."
With files from The Associated Press
