By the CNN Wire Staff
(CNN) -- The U.S. Coast Guard will attempt to set fire Wednesday to part of the huge oil slick off the coast of Louisiana, Petty Officer Steve Leeman told CNN.
It's likely the operation will begin between 11 a.m. and noon (noon and 1 p.m. ET), Leeman said.
The oil is from a rig that exploded and sank last week in the Gulf of Mexico.
Officials said the oil spill has the potential to become one of the worst in U.S. history. Oil is leaking at a rate of about 42,000 gallons a day from the well, some 50 miles off Louisiana.
A drilling rig, the Deepwater Horizon, exploded and sank at the site last week. Eleven workers are still missing after the explosion, and a search for them was suspended Friday.
Another 115 other people were rescued. One injured person remains hospitalized. The cause of the blast remains under investigation.
BP, the well's owner, has been trying to shut off the well using eight remote-controlled submarines, but it has had no luck up to this point.
"If we don't secure the well, this could be one of the most serious oil spills in U.S. history," Coast Guard Rear Adm. Mary Landry, head of a joint response task force, said at a press conference Tuesday afternoon.
The Coast Guard stressed it would never set the entire spill on fire at once. It would instead use a 500-foot-long, flame-retardant boom to gather some of the oil and then burn only the crude inside its perimeter, according to spokeswoman Lt. Sue Kerver.
Officials said oil slicks are sometimes set on fire, especially when they are near sensitive marsh areas where heavy equipment used to clean the spill may cause more harm than good.
The spill, measured from end to end, stretched as wide as 42 miles by 80 miles, although oil isn't necessarily covering that entire area.
Most of the slick is a thin sheen on the water's surface, ranging in thickness from a couple of molecules to the equivalent of a layer of paint. About 3 percent of it is a heavy, pudding-like crude oil.
At its current flow rate, it would take more than 260 days to rival the Exxon Valdez disaster, which discharged some 11 million gallons into Alaska's Price William Sound. Still, even if it never compares in size to the Exxon Valdez spill, if it makes landfall it could have serious ecological repercussions.
The Coast Guard, BP and the rig's owner, Transocean, have deployed nearly 50 vessels to help contain and clean the slick.
Marine life has been spotted in the area. Over the weekend, a plane from the U.S. Fish and Wildlife Service sighted five small whales nearby.
Efforts are also under way near the shoreline to deal with the spill should it reach land, including positioning boom material around sensitive ecological areas.
Five staging areas have been set up on land, stretching from Venice, Louisiana, to Pensacola, Florida.
Landry said it appears the slick should remain at sea for at least the next three days, although weather reports for the latter part of that period suggest the wind could shift and blow the slick toward land.
The oil, if it stays at sea, eventually will evaporate, break down and sink, or get cleaned up, but analysts have said the spill could have political fallout, especially if it reaches shore.
Lawmakers and interest groups have led a charge over the last several years to open up more parts of the U.S. coast for oil drilling.
But support for those efforts could erode if crude oil starts washing up on the Louisiana or Mississippi coasts.
The well is expected to continue leaking until it is sealed. The leak appears to be coming from a pipe that ran from the well head to the drilling rig, which is now upside down in 5,000 feet of water.
It has not been decided if the rig will be salvaged or remain where it is, a Transocean official said this week.
To seal the leak, three approaches are being tried.
BP is using remote-controlled submarines to activate the well's blowout preventer, a steel device the size of a small house that sits atop the well and is intended to choke off the flow of oil in the event of a disaster. It's not clear why that device didn't originally act to cap the well, or if it will be of any use in the future.
BP also is bringing in another drilling rig that could seal the well, but that effort would take months, according to a company spokesman.
In the meantime, BP also is trying a novel approach to capture the oil -- using a dome right above the well head. The dome resembles an inverted funnel, with a pipe leading up to ships waiting at the surface to capture the oil. That tactic has never been tried in deep water before.
A BP spokesman said the dome should be ready in two to four weeks.
CNN