Bad weather grounded planes trying to break up a giant Gulf of Mexico oil spill yesterday and forced back boats trying to scoop up and contain the slick as US President Barack Obama planned a trip to assess the disaster.

The White House said Obama would travel to the Gulf today to survey the giant oil spill washing onto Louisiana shores yesterday, raising fears of an environmental and economic catastrophe rivalling Hurricane Katrina.

The US President will be keen to avoid the fallout that followed his predecessor George W. Bush's disastrous response to the 2005 hurricane, which devastated New Orleans.

As environmentalists warned that the oil could devastate Louisiana's fragile coastline, the slick forced the operators of two natural gas platforms to order a halt to production.

Workers were evacuated from one of the platforms amid fears that the combustible oil sheen surrounding them could pose a safety risk, officials from the Minerals Management Service (MMS) told AFP.

It was believed to be the first time that production elsewhere in the Gulf has been affected by the spill, although officials said the amounts involved represented only a tiny fraction of the area's gas production.

As an estimated 200,000 gallons of oil a day spews into the Gulf of Mexico, British Petroleum spokes-man John Curry told AFP multiple efforts were underway to try and stop the flow.

"We continue to get into position to drill the relief well, that drilling begins today," he said, cautioning that the process could take up to 90 days.

Chemical dispersant also was being used underwater, while remote-controlled subs were trying to activate a blow-out preventer that should have blocked oil from flowing into the sea when the Deepwater Horizon rig sunk on April 22, two days after the platform exploded, killing 11 workers.

"We don't know why it hasn't activated. We've had these remote-controlled subs down there that have been trying to pump it full of hydraulic fluid to get it to activate. That has not succeeded so far," Curry said.

Meanwhile, the Mobile Press-Register reported yesterday that the US Coast Guard now feared the leak could become an unchecked gusher shooting out millions of gallons of oil per day.

Citing a confidential National Oceanic and Atmospheric Administration report, the Alabama newspaper said two additional release points had been found.

"If the riser pipe deteriorates further, the flow could become unchecked, resulting in a release volume an order of magnitude higher than previously thought," the paper quotes the report as saying.

That suggested the flow could be 10 times greater than estimated, the paper said.

At the Gulf well's current estimated rate of leakage, it would take 54 days for the amount of spilled toxic crude to surpass the 11 million gallons of oil that poured from the grounded Exxon Valdez tanker in Alaska in 1989.

Last Friday, US federal and state officials warned BP, which leased the rig from Transocean, that its resources appeared insufficient for the task at hand.

"I do have concerns that BP's resources are not adequate," said Louisiana Governor Bobby Jindal. "I urge them to seek more help from the federal government and others."

So far, the disaster has prompted Louisiana, Florida, Alabama and Mississippi to declare states of emergency.

The oil's approach also forced Louisiana to close shrimping grounds and oyster beds, as a massive effort involving state, federal and BP resources struggled to combat the slick.

The spill measured at least 1,500 square kilometers last Wednesday when the coast guard said oil was leaking at a rate of 5,000 barrels a day, five times faster than initially reported.

The White House has put new domestic offshore oil drilling on hold until the disaster has been fully investigated, and sent teams to the Gulf Coast "to inspect all deep water rigs and platforms to address safety concerns".

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