BRITISH Petroleum downplayed the possibility of a catastrophic accident at an offshore rig that exploded, causing the worst US spill in decades along the Gulf coast and endangering shoreline habitat.

In the 52-page exploration plan and environmental impact analysis, BP repeatedly suggested it was unlikely, or virtually impossible, for an accident to occur that would lead to a giant crude oil spill and serious damage to beaches, fish, mammals and fisheries.

At the rate the oil is pouring from the sea floor, the leak could eclipse the worst oil accident in US history - the 11 million gallons (41 million liters) that spilled from the supertanker Exxon Valdez off Alaska in 1989 - in just two months.

The spill - a slick more than 130 miles (200 kilometers) long and 70 miles (112 kilometers) wide - threatens hundreds of species of wildlife, including birds, dolphins and the fish, shrimp, oysters and crabs that make the Gulf Coast one of the nation's most abundant sources of seafood. Louisiana closed some fishing grounds and oyster beds because of the risk of oil contamination.

BP's plan filed with the federal Minerals Management Service for the Deepwater Horizon well, dated February 2009, says repeatedly that it was "unlikely that an accidental surface or subsurface oil spill would occur from the proposed activities."

And while the company conceded that a spill would "cause impacts" to beaches, wildlife refuges and wilderness areas, it argued that "due to the distance to shore (48 miles) and the response capabilities that would be implemented, no significant adverse impacts are expected."

"Clearly, the sort of occurrence that we've seen on the Deepwater Horizon is clearly unprecedented," BP spokesman David Nicholas told The Associated Press yesterday. "It's something that we have not experienced before ... a blowout at this depth."

Robert Wiygul, a Mississippi-based environmental lawyer and board member for the Gulf Restoration Network, said he doesn't see anything in the document that suggests BP addressed the kind of technology needed to control a spill at that depth of water.

"The point is, if you're going to be drilling in 5,000 feet (1,500 meters) of water for oil, you should have the ability to control what you're doing," he said.

Amid increased fingerpointing yesterday, high winds and choppy seas frustrated efforts to hold back the oil spill seeping into Louisiana's rich fishing grounds and nesting areas, while the government desperately cast about for new ideas for dealing with the growing environmental crisis.

President Barack Obama halted any new offshore drilling projects unless rigs have new safeguards to prevent a repeat of the disaster.

With the government and BP running out of options, US Interior Secretary Ken Salazar said he asked other companies across the oil and gas industry "to bring their global expertise to the situation to make sure that no idea worth pursuing is not pursued."

BP likewise sought ideas from some of its rivals and planned to use at least one of them yesterday - applying chemicals underwater to break up the oil before it reaches the surface. That has never been attempted before at such depths.

The seas were too rough and the winds too strong yesterday to burn off the oil, suck it up effectively with skimmer vessels, or hold it in check with the miles (kilometers) of orange and yellow inflatable booms strung along the coast.

The floating barriers broke loose in the choppy water, and waves sent oily water lapping over them.

Many of the more than two dozen lawsuits filed in the wake of the explosion claim it was caused when workers for oil services contractor Halliburton Inc. improperly capped the well. Halliburton denied it.

According to a 2007 study by the federal Minerals Management Service, which examined the 39 rig blowouts in the Gulf of Mexico between 1992 and 2006, cementing was a contributing factor in 18 of the incidents. In all the cases, gas seepage occurred during or after cementing of the well casing, the MMS said.

At least 1.6 million gallons (22 million liters) of oil have spilled, according to Coast Guard estimates.

As of yesterday, only a sheen of oil from the edges of the slick was washing ashore, and other extreme southeastern portions of Louisiana. But several miles (kilometers) out, the normally blue-green gulf waters were dotted with sticky, pea- to quarter-sized brown beads with the consistency of tar.

High seas were in the forecast through Sunday and could push oil deep into the inlets, ponds, creeks and lakes that line the boot of southeastern Louisiana. With the wind blowing from the south, the mess could reach the Mississippi, Alabama and Florida coasts by Monday.

"These next few days are critical," Louisiana Gov. Bobby Jindal warned.

For days, crews have struggled without success to activate the well's underwater shutoff valve using remotely operated vehicles. They are also drilling a relief well in hopes of injecting mud and concrete to seal off the leak, but that could take three months.

Salazar said he pressed the chief executive of BP to "work harder and faster and smarter to get the job done." He said the government will not rest until BP seals the well and "they clean up every drop of oil."

As for the cause of the accident, he said: "I am confident we will get to the bottom of what happened here. Those responsible will be held accountable."

In the search for creative solutions to the problem, the state of Louisiana opened gates built into the Mississippi River levees in hopes that the rush of fresh water would drive the oil away from the coast. But the tactic did not appear to work.

More than 1,900 people, some 300 vessels and dozens of aircraft took part in the effort to contain the slick, Homeland Security Secretary Janet Napolitano said. The Pentagon authorized two massive Air Force C-130 Hercules cargo planes to join civilian craft that have been dumping tens of thousands of gallons of oil-dispersing chemicals.

An animal rescue operation at Fort Jackson, southeast of New Orleans, had its first patient yesterday, a bird covered in thick, black oil. The bird, a young northern gannet found offshore, is normally white with a yellow head.

Across the state line in Mississippi, scientists, veterinarians and researchers at the Institute for Marine Mammal Studies worked frantically to prepare for the possible arrival of hundreds of oily sea mammals. The institute has surgery and exam rooms, eight large pools, and X-ray and ultrasound equipment.

Dr. Moby Solangi, the nonprofit center's director, said this is birthing season for the roughly 5,000 dolphins along the Mississippi and Louisiana coasts.

Ten sites that the American Bird Conservancy considers globally important bird areas are directly in the path of the oil slick, the group said.

President Obama, who recently announced plans to open large swaths of the US coast to offshore oil exploration, ordered Salazar to report within 30 days on what new technology is needed to tighten safeguards against spills from deepwater drilling.

"Let me be clear: I continue to believe that domestic oil production is an important part of our overall strategy for energy security," Obama said. "But I've always said that it must be done responsibly for the safety of our workers and our environment."