A Taiwanese supertanker skimmed oil from the Gulf of Mexico Saturday as the months-long disaster became the worst accidental spill on record.
Rough seas and strong winds continued to delay clean-up efforts, displace protective booms and push the oil deeper into fragile coastal wetlands, endangering wildlife preserves and the thousands of birds nesting there.
"This is going to be a very long and arduous clean-up operation in the days to come," said Coast Guard Admiral Paul Zukunft.
"I'm especially concerned with some of the wildlife habitats."
An estimated 35,000 to 60,000 barrels of oil per day has been gushing out of the ruptured well since the BP-leased Deepwater Horizon drilling rig sank on April 22, some 50 miles (80 kilometers) off the coast of Louisiana.
A containment system has captured about 557,000 barrels of oil, but rough seas have delayed the deployment of a third vessel which is set to increase capacity from 25,000 barrels to 53,000 barrels a day.
That means an estimated 1.9 to 3.6 million barrels -- or 79.5 to 153 million gallons -- of oil has now gushed into the Gulf.
Using the high end of that estimate, the spill has now surpassed the 1979 Ixtoc blowout which took nine months to cap and dumped an estimated 3.3 million barrels (140,000 million gallons) into the Gulf of Mexico.
It is topped only by the deliberate release of six to eight million barrels of crude by Iraqi troops who destroyed tankers and oil terminals and set wells ablaze in Kuwait during the 1991 Gulf War.
And it will likely be mid-August at the earliest before the Gulf well is permanently capped by injecting mud and cement with the aid of relief wells.
The Taiwanese supertanker dubbed "A Whale" could radically increase the amount of oil crews are able to recover.
"It ingests oil and oily water and then separates out the oil and expels the water," BP spokesman Toby Odone told AFP.
The giant ship, which has cuts in its sides, is some 300 yards (275 meters) long and can suck up 21 million gallons of oily water a day.
The small skimming boats which have been patrolling the Gulf for the past 10 weeks have only collected 28.2 million gallons of oily water to date.
The tanker began initial skimming operations Friday, with crews testing whether it could safely handle and dispose of the oil, but it will take several days before a final deployment decision is made, Odone said.
Rough seas caused by the first hurricane of the Atlantic season have kept the thousands of ships hired to skim oil, lay boom, carry out controlled burns, and move equipment in harbor since Tuesday.
Skimmers had been collecting about 12,000 barrels of oil a day before they were sent back to port while about 8,000 barrels of oil was being burned off the surface.
Around 450 miles (725 kilometers) of US shorelines have now been oiled as crude spews into the sea at an alarming rate, 73 days into the worst environmental disaster in US history.
A third containment ship aimed at doubling the amount of oil captured from a rupture well in the Gulf of Mexico should hopefully be working by Wednesday, said Admiral Thad Allen, who oversees operations.
The deployment of the Helix Producer is set to increase capacity from about 25,000 to 53,000 barrels of oil per day.
Officials will have a better estimate on the actual flow rate once the Helix Producer is attached "just by the visual evidence of how much oil is actually coming out around that cap," Allen said.
They will then have to decide if the existing system should stay in place, or if it would be best to undergo a risky procedure to replace the cap with another system capable of capturing up to 80,000 barrels of oil a day.
"The decision window associated with that would be sometime in the next I would say seven to 10 days," Allen said in a conference call Friday.
A key advantage of the new system is that it would greatly reduce the amount of time oil would be gushing freely into the sea if crews had to evacuate the spill site due to a bad storm.
"All of this is being weighed very, very carefully," Allen said.
Meawhile, a US government agency warned the Florida Keys and resort beaches of Miami and Fort Lauderdale were at high risk from the Gulf of Mexico oil spill.
The National Oceanic and Atmospheric Administration used a computer model to estimate the likelihood that toxic crude will ride the Loop Current into the Gulf Stream, which whips around the southern tip of Florida and up the eastern US seaboard.
The study found that much of Florida's western coastline along the Gulf "has a low probability (one to 20 percent) for impact," while the Florida Keys, Miami, and Fort Lauderdale areas "have a greater probability (61 to 80 percent)."