VENICE, Louisiana (Reuters) - Lawmakers and local residents clamored on Sunday for BP and the Obama administration to do more to save the Gulf Coast from an out-of-control oil spill that has become the biggest environmental catastrophe in the country’s history.

One congressman called the nearly six-week oil gush in the Gulf of Mexico an “environmental crime,” while a Louisiana senator demanded BP invest $1 billion immediately to protect the region’s treasured marshlands.

The failure on Saturday of a “top kill” technique attempted by London-based BP to try to seal its leaking Gulf well has unleashed a surge of anger and frustration that poses a major domestic challenge for President Barack Obama.

Obama, who has called the leaking BP well a “man-made disaster,” is trying to fend off criticism that his administration acted too slowly in its response to the spill, now known to be the worst in U.S. history.

He is in a bind because it appears only BP can stop the leak, although he has made clear the government is in charge. But critics say he has not directed enough resources to the unfolding disaster and he has been present enough.

The White House said on Sunday that the government will triple clean-up resources in areas affected by the spill, while the administration’s top energy and environment officials head back to the Gulf this week following Obama’s second visit on Friday.

“This is probably the biggest environmental disaster we have ever faced in this country,” top White House energy adviser Carol Browner told NBC’s “Meet the Press.”

BP, its reputation and market value already battered by the catastrophic spill, and the entire U.S. oil industry face more probing questions about why safety backups did not accompany their pursuit of oil in ever deeper offshore waters.

“I think without question if the word criminal should be used in terms of an environmental crime against our country, that what’s going on in the Gulf of Mexico is going to qualify,” U.S. Representative Ed Markey told CBS’ “Face the Nation.”

Department of Justice officials are part of an ongoing federal investigation into the April 20 rig explosion that triggered the spill, and the Obama administration has not ruled out the possibility of a criminal prosecution.

In Louisiana, which has borne the brunt of the oil spill impact so far, local authorities demanded that BP and the federal government rush a plan to create a sand barrier to the oil by dredging and building up outlying sandbanks and islets.

“I’m devastated ... We are dying a slow death, every time that oil takes out a piece of the marsh, a piece of Louisiana is gone forever,” said Billy Nungesser, president of Plaquemines Parish, where the oil has clogged wetlands.

“Even the government seems powerless and all the experts. If these people can’t stop it, then who in the name of God can?” Father Gerry, a priest at St. Patrick Catholic Church in Port Sulphur, Louisiana, said, his voice heavy with emotion.

‘OIL COMING UP UNTIL AUGUST’

After giving up on Saturday an attempt to pump heavy fluids and blocking materials into the leaking well to “kill” it, BP is pursuing another option from its undersea toolbox.

But BP warns that the new procedure, which will try to fit a containment cap over the leaking well, could take between four and seven days. Even then success is not guaranteed because it has never been attempted before at the depth -- a mile down -- where the oil is leaking.

BP Managing Director Robert Dudley told NBC’s “Meet the Press” the company would know by the end of the week whether the new containment effort worked.

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The next BP step would involve undersea robots using diamond-rimmed saws to cut off a pipe over the well to put in place a containment device that would try to siphon off most of the leaking oil and gas up to a tanker ship on the surface.

Dudley said he did not think BP CEO Tony Hayward, who has faced heavy criticism, should be forced to resign.

A surer solution to the leak, a relief well already being drilled, is not expected to be finished until early August.

This means crude oil continues to spew out daily, feeding a huge, fragmented slick that has already polluted marshlands teeming with wildlife and rich fisheries in Louisiana.

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“There could be oil coming up until August.” Browner told CBS’s “Face The Nation,” “We are prepared for the worst.”

Louisiana Senator Mary Landrieu called on BP to immediately invest $1 billion to protect marshes, wetlands and estuaries across the region. “While we may not be able to plug the leaking well right away, there is nothing that should stop us from getting help to the Gulf Coast immediately,” she said.

OBAMA’S ‘KATRINA’?

Gulf residents fear the spilled oil could be whipped further inshore by what promises to be the most active Atlantic storm season since 2005, the year of Hurricane Katrina.

That deadly storm proved a political disaster for President George W. Bush, who was accused of complacency in handling it, and Obama is fighting to prevent the Gulf spill from becoming his own “Katrina” ahead of the November congressional elections.

Louisianans still recovering from Katrina’s devastation were frustrated by the oil spill response. “It’s been a screw-up from day one. Nothing was at the ready and no one was in a position to respond,” said Claude Marquette, a retired physician, 68, speaking as he sat with his wife in his boat.

BP’s Hayward had predicted that despite risks, the “top kill” had a 60 to 70 percent chance of success. He said he did not know why it failed to stop the gusher.

The misstep is likely to drive his credibility lower, along with his company’s market value, which has dropped by 25 percent since the Deepwater Horizon rig exploded on April 20, killing 11 workers, and triggering the spill.

The government estimated last week that 12,000 to 19,000 barrels (504,000 to 798,000 gallons/1.9 million to 3 million liters) a day are leaking from the well. At that rate, the government now knows that the Gulf disaster has surpassed the 1989 Exxon Valdez spill in Alaskan waters.