Houston - BP Plc said on Saturday its complex "top kill" plan to plug the Gulf of Mexico oil well has failed, crushing hopes for a quick end to the largest oil spill in US history already in its fortieth day.
It may be another two months before the London-based energy giant can definitively turn off the gusher -- a delay that could undermine US President Barack Obama as he faces growing criticism for a perceived slow response to the disaster.
"We will continue to pursue any and all responsible means of stopping this leak until the completion of the two relief wells currently being drilled," Obama said in a statement after the news, noting that the wells will take months to complete.
The beleaguered BP said its next option is a "lower marine riser package" that will not plug the well ruptured in a rig blast, but rather capture most of the oil on the sea floor and channel it to the surface for collection.
BP Chief Executive Tony Hayward called the containment cap "the best way to minimize the flow of oil into the Gulf" and said it would take around four days to put it in place.
But even Obama sought to lower expectations for this option, which he said is difficult and "has never been attempted before at this depth",
BP and Hayward's credibility are at new lows, after the chief executive had given the top kill a 60 to 70 percent chance of success although it had never been done at the depth of the well, a mile (1.6 km) beneath the sea.
"I am disappointed this operation did not work," Hayward said in a statement. "The team executed the operation perfectly and the technology worked without a single hitch."
The news was a blow to Gulf coast residents, whose communities are still recovering from the 2005 Hurricane Katrina and now have to contend with oil invading fragile marshlands and waters vital to wildlife and a lucrative commercial fishing industry.
Louisiana's Plaquemines Parish president Billy Nungesser was about to address a crowd when he got news of the top kill failure. "I didn't have the heart to tell them it didn't work," he told CNN.
The Deepwater Horizon rig exploded on April 20, killing 11 workers and unleashing an underwater torrent of oil that the government estimated at 12 000 to 19 000 barrels (504,000 to 798,000 gallons/1.9 million to 3 million liters) a day.
This week, the government showed that the Gulf disaster has surpassed the 1989 Exxon Valdez spill in Alaskan waters.
'Get relief well drilled'
The bad news came over the beginning to a three-day weekend at a daily briefing by the US Coast Guard and BP Chief Operating Officer Doug Suttles.
Coast Guard Admiral Mary Landry said the failure was very disappointing and that the best option for ending the spill was the current drilling of a relief well which BP estimates will be finished by late July or early August.
Local residents angered by the string of failures and insufficient clean-up over nearly six weeks felt the same way.
"I knew it wasn't going to work," said Joey Toups, 53, a Louisiana shrimper idled by the spill and a former oil worker.
"I've worked in oil fields before. The only solution is that other drilling rig sitting out there. They need to get the relief well drilled."
BP's already tarnished reputation and its bottom line are likely to suffer further, as is the share price when markets re-open on Tuesday.
BP has thus far spent $940 million to try to plug the leak and clean up the sea and soiled coast.
The disaster has wiped out a quarter of its market value, or $50bn, and its London-traded shares lost 5 percent on Friday alone as delays in the top kill made investors sell.
Top kill involved pumping heavy fluids known as drilling mud and other material into the well shaft to stifle the flow, then seal it with cement. Hayward said BP pumped 30,000 barrels of mud at high pressure before giving up.
Although the Obama administration has put the blame squarely on BP, polls show Americans are losing faith in the government's ability to mitigate the disaster.
In his second visit to the Gulf in the 40-day crisis on Friday, Obama faced criticism that he responded too slowly. He told people in Louisiana that they "will not be left behind" and that the "buck stops" with him.
There is not much Obama can do other than apply pressure to BP to get it right and put his best scientists in the room. The government has no deep-sea oil technology of its own.
Comparisons to Katrina
But that does not mean the public will forgive the first-term president, who is anxious to avoid comparisons to former President George W. Bush and his government's much-criticized response to Hurricane Katrina.
His political opponents, and even some prominent Democrats, are calling on him to take command of the situation. That kind of rhetoric could hurt his credibility ahead of congressional elections in November, when Democrats are poised to lose seats.
Obama again tried to assuage Gulf residents on Saturday and told them he will keep the heat on BP to repair the damage to their lives and habitat.
"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 his statement.
With the leak and the clean-up far from solved, BP now has a new headache: accusations that its 22 000 workers employed in clean-up are not adequately trained and equipped and some of them have been sickened by the oil.
Suttles said, "It's clear that people have gotten sick and we need to figure out what we need to do to change that." But he said illness was not widespread among the workers.