MIAMI (Reuters) - The Coast Guard is scrambling to prevent a giant slick from an oil rig blowout from reaching the U.S. Gulf of Mexico shoreline, Coast Guard Commandant Admiral Thad W. Allen said on Wednesday.
"This is potentially a very serious issue ... We are under no illusion of the risk that's involved here," Allen said.
He told reporters in Miami the Coast Guard, working with federal and local authorities, had activated contingency measures aimed at protecting at-risk areas of the coast line, such as nature wetlands, from the spill.
But the slick could still threaten the coasts of eastern Louisiana, Mississippi and Alabama, Allen said, adding that there was no immediate risk to south Florida.
"The best projection is that there would be no impact on the shoreline for three days," Allen said, repeating forecasts that the spilled oil would not reach shore until the weekend.
"It depends on the weather and what the trajectory is," said Allen, who spoke after addressing a maritime security conference in Miami.
The Coast Guard said on Tuesday that the crude slick had a circumference of about 600 miles, covering about 28,600 square miles (74,070 sq km). That is slightly bigger than the U.S. state of West Virginia.
Allen said the Coast Guard was currently deploying fire retardant booms and considering the option of setting the oil slick ablaze, in what he called an "in situ burn," to dissipate it.
At the same time, London-based BP Plc, which owns the well and is financially responsible for the cleanup, was concentrating its efforts on trying to cut off the flow from the blown-out offshore well, by shutting off an undersea valve.
BP is also drilling a so-called relief well. But Allen stressed that these efforts were taking place at a depth of 5,000 feet and said the entire sealing and relief operation could take between 45 and 90 days.
Editing by Tom Brown and Alden Bentley