Thousands of barrels of oil continue to spill into the Gulf of Mexico as BP's latest control efforts have failed to stem what is now the largest offshore oil spill in United States history.

The U.S. government has estimated that some 18 to 40 million gallons of oil have been dumped into the Gulf since April 20's explosion of the Deepwater Horizon oil rig, far exceeding the 11 million gallons lost in the 1989 Exxon Valdez spill.

Scientists at the U.S. Geological Survey have refuted BP's claims that 5,000 barrels of oil are spilling each day, and say the real figures are somewhere between 12,000 and 19,000 barrels.

On Saturday, BP announced that its bid to "top kill" the leak by plugging it with debris and heavy drilling mud had failed after three days of effort.

The oil giant is now saying that they will try to saw off part of the broken pipe and place a cap on the end using remotely guided undersea robots.

The strategy is similar to BP's first failed control effort, which involved a large containment dome that became unusable after it was clogged with ice.

The company has said they have learned from that failure, and will be using warm water to avoid ice problems.

But BP's failure to contain the leak after six weeks of efforts have left politicians and much of the public with little confidence in the oil company's abilities to stop the spill.

"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," Rep. Ed Markey (D-Mass.) told CBS News.

According to President Obama, however, who visited the Gulf Coast on Friday for the second time since the spill began, the government is in control of the clean-up efforts and will make sure that they are completed.

"[The spill] 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 on Saturday.

Meanwhile, the Rev. Katharine Jefferts Schori, presiding bishop of the Episcopal Church has cited the "still-unfolding disaster in the Gulf of Mexico" as evidence that "we are all connected, and that harm to one part of the sacred circle of life harms the whole."

"[The oil spill] has its origins in this nation's addiction to oil, uninhibited growth, and consumerism, as well as old-fashioned greed and what my tradition calls hubris and idolatry," Schori wrote in an entry in the Huffington Post. "Our collective sins are being visited on those who have had little or no part in them: birds, marine mammals, the tiny plants and animals that constitute the base of the vast food chain in the Gulf, and on which a major part of the seafood production of the United States depends."

"Our sins are being visited on the fishers of southern Louisiana, Mississippi, Alabama, and Florida, who seek to feed their families with the proceeds of what they catch each day," she continues. "Our sins will expose New Orleans and other coastal cities to the increased likelihood of devastating floods, as the marshes that constitute the shrinking margin of storm protection continue to disappear, fouled and killed by oil."

"There is no place to go 'away' from these consequences; there is no ultimate escape on this planet. The effects at a distance may seem minor or tolerable, but the cumulative effect is not," she says.

"We are all connected, we will all suffer the consequences of this tragic disaster in the Gulf, and we must wake up and put a stop to the kind of robber baron behavior we supposedly regulated out of existence a hundred years ago. Our lives, and the liveliness of the entire planet, depend on it."