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 Sunday, 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.