NEW ORLEANS - Gulf of Mexico cleanup crews working to block millions of gallons of oil from reaching land may soon have a giant on their side, if a weekend test of a new skimmer goes well.

The Taiwanese vessel dubbed "A Whale," which its owners describe as the largest oil skimmer in the world, began showing its capabilities on Saturday just north of the Macondo Deepwater well site. An April 20 explosion on the Deepwater Horizon rig there killed 11 workers and began what is now the largest oil spill in Gulf history.

The vessel will cruise a 25-square-mile test site through today, according to TMT Shipping, the company that created A Whale by retrofitting an oil tanker after the explosion sent millions of gallons of crude spilling into the Gulf.

The U.S. Coast Guard, along with BP, are waiting to see if the vessel, which is 10 stories high and as long as 3 1/2 football fields, can live up to its makers' promise of being able to process up to 21 million gallons of oil-fouled water a day.

The ship works by taking in water through 12 vents, separating the oil and pumping the cleaned seawater back into the Gulf.

"In many ways, the ship collects water like an actual whale and pumps internally like a human heart," TMT spokesman Bob Grantham said in an e-mail.

A Whale is being tested close to the wellhead because officials believe it will be most effective where the oil is thickest rather than closer to shore.

The ship arrived in the Gulf on Wednesday, but officials have wanted to test its capability as well as have the federal Environmental Protection Agency sign off on the water it will pump back into the gulf. Although the ship cleans most of the oil from seawater, trace amounts of crude remain.

The wait has frustrated some local officials, who say the mammoth skimmer would be a game-changer in preventing drifting streams of oil from washing ashore on vulnerable coastlines.

During a Thursday tour of the inlet to Barataria Bay, Louisiana Gov. Bobby Jindal said it was exasperating to have A Whale anchored offshore instead of being put to immediate use.

"They've used the war rhetoric," Jindal said aboard a Louisiana state wildlife boat floating in oil-slicked waters near Grand Isle. "If this is really a war, they need to be using every resource that makes sense to fight this oil before it comes to our coast."

A smaller flotilla of oil skimmers was back at work along the Gulf coast Saturday, after being forced to stand down for several days because of nasty weather whipped up by distant Hurricane Alex.