President Barack Obama returns to the endangered Gulf of Mexico coast Friday, as oil giant BP now says it needs two more days before it knows whether it has clamped shut a broken well that has gushed millions of gallons (liters) of crude for more than a month.
Obama is making his second visit to the Gulf shore, where oil now washes ashore _ killing wildlife, fouling fragile wetlands and marring white sand beaches. On Thursday, Obama took responsibility for stopping the spewing well but admitted the U.S. government doesn't have the technology or expertise for the job and must rely on BP.
On Friday morning, BP PLC CEO Tony Hayward said it would be about 48 hours before it can be known if pumping heavy mud into the blown-out well is successful in stopping what is now the worst U.S. oil spill. Hayward said on CBS television's "Early Show" that his confidence level in the well-plugging effort remains at 60 to 70 percent.
BP, the largest oil and gas producer in the United States, began injecting mud into the well on Wednesday in an untested effort to end a spill that has surpassed the Exxon Valdez disaster since it started after an oil rig explosion April 20 that killed 11 workers.
The maneuver, called a top kill, has worked on land but has never been tried in deep water.
The Obama administration's point man on the disaster, Coast Guard Adm. Thad Allen, said BP's work Friday will tell if a cap can hold.
Allen told ABC's "Good Morning America" that the mud pumped into the well has pushed the oil down, but the challenge is going to be to keep enough pressure on the oil flow to put a cement plug in place.
"The real question is, can we sustain it, and that'll be the critical issue going through the next 12 to 18 hours," Allen said.
As the world waited, Obama announced major new restrictions on drilling projects, and the head of the federal agency that regulates the industry resigned under pressure, becoming the highest-ranking political casualty of the crisis so far.
Obama was to attend a briefing Friday at the U.S. Coast Guard Station in Grand Isle, Louisiana, by Allen.
Obama seized ownership Thursday of what he called a "tremendous catastrophe," after weeks of allowing Cabinet members to take the public lead as the crippled BP well spewed millions of gallons (liters) of crude oil into the Gulf from nearly a mile (1,600 meters) below the surface.
"I take responsibility. It is my job to make sure that everything is done to shut this down," Obama declared at a White House news conference dominated by the spill.
For everyone, the stakes grew even higher Thursday as government scientists said the oil has been flowing at a rate 2 1/2 to five times higher than what BP and the U.S. Coast Guard initially estimated.
Two teams of scientists calculated the well has been spewing between 504,000 gallons (1.9 million liters) and more than 1 million gallons (3.8 million liters) a day. Even using the most conservative estimate, that means about 18 million gallons (68 million liters) have spilled so far. In the worst-case scenario, 39 million gallons (148 million liters) have leaked.
Even at the lowest estimate, the Gulf spill has far surpassed the size of what had been the largest U.S. oil spill, the 1989 Exxon Valdez disaster. The tanker by that name ran aground in Alaska, spilling nearly 11 million gallons (42 million liters).
The spill is not the biggest ever in the Gulf. In 1979, a drilling rig in Mexican waters _ the Ixtoc I _ blew up, releasing 140 million gallons (530 million liters) of oil.
Hayward said on CBS that things were progressing as planned. He said BP engineers had completed a second phase by pumping what he called "loss prevention material" into the blowout preventer, a massive piece of machinery that sits atop the well. That material was supposed to form "a bridge against which we could pump" more heavyweight mud inside the blowout preventer.
That part of the operation was completed early Friday and appeared to have been partially successful. BP would go back to pumping more mud later Friday, he said.
If the mud works, BP would pour cement to seal the well.
"Clearly I'm as anxious as everyone in America is to get this thing done," Hayward said.
If the top kill fails, BP's next best hope for controlling even part of the leak is a tinier version of something that has already been tried: a steel containment box to cap the well. A 100-ton box lies junked on the ocean floor, abandoned by BP after ice-like crystals clogged it.
While BP officials say the smaller box shouldn't have that problem, it's clearly not their preferred method. It has been sitting in reserve on the seabed for more than a week while engineers first tried to siphon off oil through a mile-long (1.6-kilometer-long) tube.
Either way, crews will continue to drill two relief wells, considered the only surefire way to stop the leak, but that operation will take weeks to complete.
BP has spent $930 million so far responding to the ruptured well, it said in a regulatory filing Friday, including costs for clean-up and prevention work, drilling relief wells, paying grants to Gulf states, damage claims and federal costs. BP says it's too early to quantify other potential costs and liabilities associated with the spill.
In another troubling discovery, marine scientists said they have spotted a huge new plume of what they believe to be oil deep beneath the Gulf, stretching 22 miles (35 kilometers) from the leaking well head northeast toward Mobile Bay, Alabama. They fear it could have resulted from using chemicals a mile below the surface to break up the oil.
Obama took responsibility under mounting criticism _ even from members of his own Democratic Party _ for seeming aloof to what could be the biggest environmental tragedy in U.S. history.
Asked about inevitable comparisons between his administration's handling of the disaster with his predecessor's response to Hurricane Katrina in 2005, which flooded New Orleans and other areas, Obama said: "I'll leave it to you guys to make those comparisons. ... What I'm thinking about is how do you solve the problem?"
Comparisons to former President George W. Bush's paltry response to the devastating storm have come mainly from opposition Republicans.
"I'm confident people are going to look back and say this administration was on top of what was an unprecedented crisis," he said. "We've got to get it right."
He spoke shortly after the head of the troubled agency that oversees offshore drilling resigned under pressure. The departure of Minerals Management Service Director Elizabeth Birnbaum was announced just before Obama's news conference began.