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.
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 never been tried in deep water.
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 Adm. Thad Allen, who is overseeing the spill response to the spill. It would be his second inspection visit to the region.
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 television 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 operation doesn't work, the company has a number of backup plans. 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.
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."
Obama is struggling for high ground in the political wars raging in the months before the November congressional elections, where his Democratic majorities in both House and Senate are in danger.
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.
While making clear he was leading the response, Obama acknowledged some things could have been better handled.
He said his administration didn't act with "sufficient urgency" prior to the spill to clean up the Minerals Management Service, accused of corruption and poor regulation of drilling rigs and wells.
While Obama defended calling for an expansion of offshore drilling before the spill, he said he "was wrong" to believe that oil companies were prepared to respond to worst-case oil spills.
Obama also said the administration took too long to make its own measurements of the size of the spill, and didn't push BP hard enough early on to release underwater footage of the gusher.